Lead-acid battery

ABSTRACT

A lead-acid battery includes a positive electrode plate, a negative electrode plate, and an electrolyte solution. The negative electrode plate includes a negative electrode material. The negative electrode material contains a polymer compound. The polymer compound has a peak in a range of 3.2 ppm or more and 3.8 ppm or less in a chemical shift of 1H-NMR spectrum, or the negative electrode material contains a polymer compound having a repeating structure of oxy C2-4 alkylene units.

TECHNICAL FIELD

The present invention relates to a lead-acid battery.

BACKGROUND ART

Lead-acid batteries are used for various applications, includingautomotive and industrial applications. The lead-acid batteries includea negative electrode plate, a positive electrode plate, a separator (ormat), an electrolyte solution, and the like. An additive may be added toconstituent members of the lead-acid battery from the viewpoint ofimparting various functions.

Patent Document 1 proposes a lead-acid battery in which an activatorcontaining an organic polymer is enclosed in a small sealed case havinga cleavage mechanism into a container, and the small sealed case isattached to the container or a lid part.

Patent Document 2 proposes a fiber-attached mat containing a pluralityof fibers coated with a size composition, a binder composition, and oneor more additives, in which the additives include one or more of rubberadditives, rubber derivatives, aldehydes, metal salts,ethylene-propylene oxide block copolymers, sulfuric acid esters,sulfonic acid esters, phosphoric acid esters, polyacrylic acid,polyvinyl alcohol, lignin, phenol formaldehyde resins, cellulose, woodflour, and the like, and the additives can function to reduce moistureloss in a lead-acid battery.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-A-2000-149980-   Patent Document 2: JP-W-2017-525092

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

A lead-acid battery is required to have a long life. Factors thatshorten the life of the lead-acid battery include, for example,corrosion of a current collector of a positive electrode plate(hereinafter may be referred to as a positive electrode currentcollector), reduction of an electrolyte solution (hereinafter may bereferred to as a liquid decrease), and the like. The corrosion of thepositive electrode current collector and the liquid decrease proceed dueto overcharge.

Means for Solving the Problems

One aspect of the present invention relates to a lead-acid batteryincluding a positive electrode plate, a negative electrode plate, and anelectrolyte solution, in which the negative electrode plate includes anegative electrode material, the negative electrode material contains apolymer compound, and the polymer compound has a peak in a range of 3.2ppm or more and 3.8 ppm or less in a chemical shift of ¹H-NMR spectrum.

Another aspect of the present invention relates to a lead-acid batteryincluding a positive electrode plate, a negative electrode plate, and anelectrolyte solution,

in which the negative electrode plate includes a negative electrodematerial, and

the negative electrode material contains a polymer compound having arepeating structure of oxy C₂₋₄ alkylene units.

Advantages of the Invention

In the lead-acid battery, an excellent effect of reducing an amount ofcharge during overcharge is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cutaway exploded perspective view showing anappearance and an internal structure of a lead-acid battery according toone aspect of the present invention.

MODE FOR CARRYING OUT THE INVENTION

A lead-acid battery according to one aspect of the present inventionincludes a positive electrode plate, a negative electrode plate, and anelectrolyte solution. The negative electrode plate includes a negativeelectrode material. The negative electrode material contains a polymercompound. The polymer compound has a peak in a range of 3.2 ppm or moreand 3.8 ppm or less in a chemical shift of ¹H-NMR spectrum.

Note that the peak appearing in the range of 3.2 ppm or more and 3.8 ppmor less in the ¹H-NMR spectrum is derived from an oxy C₂₋₄ alkyleneunit. Here, the ¹H-NMR spectrum is measured using deuterated chloroformas a solvent.

A lead-acid battery according to another aspect of the present inventionincludes a positive electrode plate, a negative electrode plate, and anelectrolyte solution. The negative electrode plate includes a negativeelectrode material. The negative electrode material contains a polymercompound having a repeating structure of oxy C₂₋₄ alkylene units.

In the lead-acid battery according to one aspect and another aspect ofthe present invention, the negative electrode material contains thepolymer compound as described above. It is important that the negativeelectrode material contains the polymer compound regardless of whetheror not a component of the lead-acid battery other than the negativeelectrode material contains the polymer compound. When the negativeelectrode material contains the polymer compound, the polymer compoundcan be present near lead, and an effect of the polymer compound can beeffectively exhibited. With such a configuration, a hydrogen overvoltagein the negative electrode plate can be increased, so that an amount ofovercharge can be reduced. Since suppression of hydrogen generationduring overcharge can reduce liquid decrease, it is advantageous forprolonging the life of the lead-acid battery.

In general, in a lead-acid battery, the reaction during overcharge isgreatly affected by a reductive reaction of hydrogen ions at aninterface between lead and an electrolyte solution. Thus, in thelead-acid battery according to one aspect and another aspect of thepresent invention, the reason why the amount of overcharge is reduced isconsidered to be that a surface of lead which is a negative activematerial is covered with the polymer compound, so that the hydrogenovervoltage increases, and a side reaction in which hydrogen isgenerated from protons during overcharge is inhibited.

The polymer compound easily takes a linear structure by having oxy C₂₋₄alkylene units, and thus it is considered that the polymer compoundhardly remains in the negative electrode material and easily diffusesinto the electrolyte solution. Thus, it is expected that the effect ofreducing the amount of overcharge is hardly obtained even when thepolymer compound is used. However, contrary to such expectation, thepresent inventors have actually found that even when a very small amountof a polymer compound is contained in the negative electrode material,the effect of reducing the amount of overcharge can be obtained. Sinceeven a very small amount of the polymer compound can provide the effectof reducing the amount of overcharge, it is considered that when thepolymer compound is contained in the negative electrode material, thepolymer compound can be present near lead, whereby a high adsorptionaction of the oxy C₂₋₄ alkylene unit on lead is exerted. It is furtherconsidered that the polymer compound spreads thinly on the lead surfaceand the reductive reaction of hydrogen ions in a wide region of the leadsurface is suppressed. This does not contradict that the polymercompound easily takes a linear structure.

In general, in a lead-acid battery, since a sulfuric acid aqueoussolution is used as an electrolyte solution, when an organic additive(oil, polymer, organic expander, or the like) is contained in a negativeelectrode material, it becomes difficult to balance elution into theelectrolyte solution and adsorption to lead. For example, when anorganic additive having low adsorptivity to lead is used, elution intothe electrolyte solution becomes easy, so that the amount of overchargeis hardly reduced. On the other hand, when an organic additive havinghigh adsorptivity to lead is used, it is difficult to thinly adhere theorganic additive to the lead surface, and the organic additive tends tobe unevenly distributed in the lead pores.

In general, when the lead surface is covered with an organic additive,the reductive reaction of hydrogen ions hardly occurs, and therefore theamount of overcharge tends to decrease. When the lead surface is coveredwith the organic additive, lead sulfate generated during discharge ishardly eluted during charge, so that charge acceptability isdeteriorated. Thus, suppression of deterioration of charge acceptabilityand reduction in the amount of overcharge are in a trade-offrelationship, and it has been conventionally difficult to achieve bothsimultaneously. In addition, when the organic additive is unevenlydistributed in lead pores, it is necessary to increase a content of theorganic additive in the negative electrode material in order to ensure asufficient effect of reducing the amount of overcharge. However, whenthe content of the organic additive is increased, the chargeacceptability is greatly deteriorated.

When the organic additive is unevenly distributed in the lead pores,movement of ions (such as lead ions and sulfate ions) is inhibited bysteric hindrance of the unevenly distributed organic additive. Thus,low-temperature high rate (HR) discharge performance is alsodeteriorated. When the content of the organic additive is increased inorder to ensure a sufficient effect of reducing the amount ofovercharge, movement of ions in the pores is further inhibited, and thelow temperature HR discharge performance is also deteriorated.

On the other hand, in the lead-acid battery according to one aspect andanother aspect of the present invention, the polymer compound having anoxy C₂₋₄ alkylene unit is contained in the negative electrode material,so that the lead surface is covered with the polymer compound in thethinly spread state as described above. Thus, as compared with the caseof using other organic additives, even when the content in the negativeelectrode material is small, an excellent effect of reducing the amountof overcharge can be secured. Since the polymer compound thinly coversthe lead surface, elution of lead sulfate, generated during discharge,during charge is less likely to be inhibited, whereby the deteriorationof the charge acceptability can also be suppressed. Thus, it is possibleto suppress the deterioration of the charge acceptability while reducingthe amount of overcharge. Since the uneven distribution of the polymercompound in the lead pores is suppressed, ions easily move, and thedeterioration of the low temperature HR discharge performance can alsobe suppressed.

In the lead-acid battery according to one aspect of the presentinvention, the polymer compound may contain an oxygen atom bonded to aterminal group and a —CH₂— group and/or a —CH< group bonded to theoxygen atom. In the ¹H-NMR spectrum, a ratio of an integrated value ofthe peak of 3.2 ppm to 3.8 ppm to the sum of the integrated value ofthis peak, an integrated value of a peak of hydrogen atoms of the —CH₂—group bonded to the oxygen atom, and an integrated value of a peak of ahydrogen atom of the —CH< group bonded to the oxygen atom is preferably85% or more. Such polymer compounds contain many oxy C₂₋₄ alkylene unitsin the molecule. Therefore, it is considered that it becomes easy toadsorb to lead, and it becomes easy to thinly cover the lead surface byeasily taking a linear structure. Thus, the amount of overcharge can bemore effectively reduced. An effect of suppressing the deterioration ofthe charge acceptability and/or the low temperature HR dischargeperformance can be further enhanced.

In the ¹H-NMR spectrum, the polymer compound having a peak in thechemical shift range of 3.2 ppm to 3.8 ppm preferably contains arepeating structure of oxy C₂₋₄ alkylene units. When a polymer compoundcontaining a repeating structure of oxy C₂₋₄ alkylene units is used, itis considered it becomes easier to adsorb to lead, and it becomes easyto thinly cover the lead surface by easily taking a linear structure.Thus, the amount of overcharge can be more effectively reduced. Aneffect of suppressing the deterioration of the charge acceptabilityand/or the low temperature HR discharge performance can be furtherenhanced.

In the present specification, the polymer compound refers to a compoundhaving a repeating unit of oxy C₂₋₄ alkylene units and/or having anumber average molecular weight (Mn) of 500 or more.

Note that the oxy C₂₋₄ alkylene unit is a unit represented by —O—R¹— (R¹represents a C₂₋₄ alkylene group).

The polymer compound may contain at least one selected from the groupconsisting of etherified products of a hydroxy compound having arepeating structure of oxy C₂₋₄ alkylene units and esterified productsof a hydroxy compound having a repeating structure of oxy C₂₋₄ alkyleneunits. Here, the hydroxy compound is at least one selected from thegroup consisting of poly C₂₋₄ alkylene glycols, copolymers containing arepeating structure of oxy C₂₋₄ alkylene, and C₂₋₄ alkylene oxideadducts of a polyol. When such a polymer compound is used, thedeterioration of the charge acceptability can be further suppressed.Since the effect of reducing the amount of overcharge is high,generation of hydrogen gas can be more effectively suppressed, and ahigh liquid decrease suppressing effect can be obtained.

The repeating structure of oxy C₂₋₄ alkylene units may contain at leasta repeating structure of oxypropylene units (—O—CH(—CH₃)—CH₂—). Such apolymer compound easily spreads thinly on a lead surface while havinghigh adsorptivity to lead, and is considered to have an excellentbalance therebetween. Thus, the amount of overcharge can be moreeffectively reduced. An effect of suppressing the deterioration of thecharge acceptability and/or the low temperature HR discharge performancecan be further enhanced.

As described above, since the polymer compound can thinly cover the leadsurface while having high adsorptivity to lead, even if the content ofthe polymer compound in the negative electrode material is small (forexample, less than 400 ppm), the amount of overcharge can be reduced.Since a sufficient effect of reducing the amount of overcharge can besecured even if the content is small, it is also possible to suppressthe deterioration of charge acceptability. The steric hindrance of thepolymer compound in the lead pores can be reduced, and a structuralchange of the negative active material due to collision of the hydrogengas can also be suppressed, so that the deterioration of the lowtemperature HR discharge performance can also be suppressed even afterhigh temperature light load test. From the viewpoint of securing ahigher effect of reducing the amount of overcharge, the content of thepolymer compound in the negative electrode material is preferably morethan 8 ppm.

The polymer compound may be contained in the electrolyte solution. Theconcentration of the polymer compound in the electrolyte solution may be500 ppm or less on a mass basis. The content of the polymer compound inthe negative electrode material may be more than 8 ppm and less than 400ppm, or may be 15 ppm or more and 360 ppm or less on a mass basis. Asdescribed above, even when the amount of the polymer compound containedin the negative electrode material and the electrolyte solution issmall, the amount of overcharge can be reduced, and the deterioration ofthe charge acceptability and/or the low temperature HR dischargeperformance can be suppressed.

The polymer compound preferably contains at least a compound having Mnof 1,000 or more. In this case, the polymer compound tends to remain inthe negative electrode material, and in addition, the adsorbability tolead is enhanced; therefore, the effect of reducing the amount ofovercharge is further enhanced. By reducing the amount of overcharge,the structural change of the negative active material due to collisionof the hydrogen gas with the negative electrode material can also besuppressed. Thus, even after the high temperature light load test inwhich the structural change of the negative active material is likely tooccur, the effect of suppressing the deterioration of the lowtemperature HR discharge performance can be enhanced.

It is also preferable that the concentration of the polymer compound inthe electrolyte solution is 100 ppm or more. At this time, the polymercompound preferably contains at least a compound having Mn of 1,000 ormore and 5,000 or less. Since the polymer compound having Mn of 5,000 orless is easily dissolved in the electrolyte solution and easily moves inthe electrolyte solution, the polymer compound moves into the negativeelectrode material and can further enhance the effect of reducing theamount of overcharge. Since the structural change of the negative activematerial due to the hydrogen gas is also suppressed, it is also possibleto suppress the deterioration of the low temperature HR dischargeperformance after the high temperature light load test. In the polymercompound having Mn of 1,000 or more, it is considered that theadsorbability to lead is further enhanced, and the effect of reducingthe amount of overcharge can be further enhanced. When the lead-acidbattery is used for a long period of time, the structural change of thenegative active material gradually proceeds, and the polymer compoundtends to be easily eluted from the negative electrode plate. However,when the electrolyte solution contains some concentration of polymercompound, elution of the polymer compound from the negative electrodeplate can be suppressed, the polymer compound can be retained in thenegative electrode material, and the polymer compound can be replenishedfrom the electrolyte solution to the negative electrode plate.

It is sufficient that the polymer compound can be contained in thenegative electrode material, and the source of the polymer compoundcontained in the negative electrode material is not particularlylimited. Similarly, the source of the polymer compound contained in theelectrolyte solution is not particularly limited. The polymer compoundmay be contained in any of the components (for example, a negativeelectrode plate, a positive electrode plate, an electrolyte solution,and/or a separator, and the like) of the lead-acid battery whenpreparing the lead-acid battery. The polymer compound may be containedin one constituent element, or may be contained in two or moreconstituent elements (for example, a negative electrode plate, anelectrolyte solution, and the like).

The negative electrode material may further contain an organic expander(first organic expander) having a sulfur element content of 2,000 μmol/gor more. When such an organic expander and the polymer compound are usedin combination, the deterioration of the charge acceptability can befurther suppressed. The charge acceptability is governed by adissolution rate of lead sulfate during charge in the negative electrodeplate. In a case where an amount of discharge is the same, when thefirst organic expander is used, a particle size of lead sulfategenerated during discharge is smaller than that when the organicexpander (second organic expander) having a small sulfur element content(for example, less than 2,000 μmol/g, preferably 1,000 μmol/g or less)is used, and a specific surface area of lead sulfate increases. Thus, inthe case of using the first organic expander, a ratio of a surface oflead sulfate covered with the polymer compound is smaller than that inthe case of using the second organic expander. Thus, it is consideredthat dissolution of lead sulfate is hardly inhibited, and thedeterioration of the charge acceptability is suppressed.

The negative electrode material may contain the second organic expander.When the second organic expander and the polymer compound are used incombination, a particle size of a colloid can be reduced, so that theeffect of suppressing the deterioration of the low temperature HRdischarge performance can be further enhanced.

The negative electrode material may contain the second organic expanderin addition to the first organic expander. When the first organicexpander and the second organic expander are used in combination withthe polymer compound, the effect of suppressing the deterioration of thecharge acceptability can be synergistically enhanced. The first organicexpander and the second organic expander form different kinds ofcolloids in the negative electrode material. At a boundary wheredifferent types of colloids are in contact with each other, adhesionbetween the colloids is lower than that at a boundary where the sametype of colloids are in contact with each other. Thus, lead ions easilypass through the boundary where different types of colloids are incontact with each other. Thus, the dissolution of lead sulfate easilyproceeds. As a result, it is considered that a synergistic effect insuppressing the deterioration of the charge acceptability is obtained.

The first organic expander may contain a condensate containing a unit ofan aromatic compound having a sulfur-containing group, and thecondensate may contain, as the unit of the aromatic compound, at leastone selected from the group consisting of a unit of a bisarene compoundand a unit of a monocyclic aromatic compound. The condensate may containthe unit of the bisarene compound and the unit of the monocyclicaromatic compound The unit of the monocyclic aromatic compound mayinclude a unit of a hydroxyarene compound. Such a condensate is moreadvantageous in suppressing the deterioration of the low temperature HRdischarge performance after the high temperature light load test becausethe low temperature HR discharge performance is not impaired even whenthe condensate experiences an environment higher than normaltemperature.

The sulfur element content in the organic expander being X μmol/g meansthat the content of the sulfur element contained per 1 g of the organicexpander is X μmol.

The content of the polymer compound in the negative electrode materialand the concentration of the polymer compound in the electrolytesolution are determined for a lead-acid battery in a fully chargedstate.

The lead-acid battery may be either a valve regulated (sealed) lead-acidbattery or a flooded-type (vented type) lead-acid battery.

In the present specification, the fully charged state of theflooded-type lead-acid battery is defined by the definition of JIS D5301: 2006. More specifically, the following state is defined as a fullycharged state: the lead-acid battery is charged at a current (A) 0.2times as large as a numerical value described as a rated capacity (Ah)until a terminal voltage during charge measured every 15 minutes or anelectrolyte solution density subjected to temperature correction to 20°C. exhibits a constant value at three significant digits continuouslythree times. In the case of a valve regulated lead-acid battery, thefully charged state is a state where the lead-acid battery is subjectedto constant current constant voltage charge of 2.23 V/cell at a current(A) 0.2 times as large as the numerical value described as the ratedcapacity (Ah) in an air tank of 25° C.±2° C., and the charge iscompleted when the charge current (A) during constant voltage chargebecomes 0.005 times as large as the numerical value described in therated capacity (Ah). Note that the numerical value described as therated capacity is a numerical value in which the unit is Ah. The unit ofthe current set based on the numerical value indicated as the ratedcapacity is A.

The lead-acid battery in the fully charged state refers to a batteryobtained by fully charging a formed lead-acid battery. The full chargeof the lead-acid battery may be performed immediately after formation solong as being performed after formation or may be performed after thelapse of time from formation (e.g., a lead-acid battery in use(preferably at the initial stage of use) after formation may be fullycharged). The battery at the initial stage of use refers to a batterythat has not been used for a long time and has hardly deteriorated.

In the present specification, the number average molecular weight Mn isdetermined by gel permeation chromatography (GPC). A standard substanceused for determining Mn is polyethylene glycol.

Hereinafter, the lead-acid battery according to an embodiment of thepresent invention will be described for each of the main constituentelements, but the present invention is not limited to the followingembodiment.

[Lead-Acid Battery] (Negative Electrode Plate)

The negative electrode plate usually includes a negative currentcollector in addition to a negative electrode material. The negativeelectrode material is obtained by removing the negative currentcollector from the negative electrode plate. Note that a member such asa mat or a pasting paper may be stuck to the negative electrode plate.Such a member (sticking member) is used integrally with the negativeelectrode plate and is thus assumed to be included in the negativeelectrode plate. Also, when the negative electrode plate includes such amember, the negative electrode material excludes the negative currentcollector and the sticking member. However, when the sticking membersuch as a mat is attached to a separator, a thickness of the stickingmember is included in a thickness of the separator.

The negative current collector may be formed by casting lead (Pb) or alead alloy, or may be formed by processing a lead sheet or a lead alloysheet. Examples of the processing method include expanding processingand punching processing. It is preferable to use a negative electrodegrid as the negative current collector because the negative electrodematerial is easily supported.

The lead alloy used for the negative current collector may be any of aPb—Sb-based alloy, a Pb—Ca-based alloy, and a Pb—Ca—Sn-based alloy. Thelead or lead alloys may further contain, as an additive element, atleast one selected from the group consisting of Ba, Ag, Al, Bi, As, Se,Cu, and the like. The negative current collector may include a surfacelayer. The surface layer and the inner layer of the negative currentcollector may have different compositions. The surface layer may beformed in a part of the negative current collector. The surface layermay be formed in the lug of the negative current collector. The surfacelayer of the lug may contain Sn or an Sn alloy.

The negative electrode material contains the above polymer compound. Thenegative electrode material further contains a negative active material(lead or lead sulfate) that exhibits a capacity through a redoxreaction. The negative electrode material may contain an expander, acarbonaceous material, and/or other additives. Examples of the additiveinclude barium sulfate, fibers (resin fibers and the like), and thelike, but are not limited thereto. Note that the negative activematerial in the charged state is spongy lead, but the non-formednegative electrode plate is usually prepared using lead powder.

(Polymer Compound)

The polymer compound has a peak in a range of 3.2 ppm or more and 3.8ppm or less in a chemical shift of ¹H-NMR spectrum. Such polymercompounds have oxy C₂₋₄ alkylene units. Examples of the oxy C₂₋₄alkylene unit include an oxyethylene unit, an oxypropylene unit, anoxytrimethylene unit, an oxy 2-methyl-1,3-propylene unit, an oxy1,4-butylene unit, an oxy 1,3-butylene unit, and the like. The polymercompound may have one kind or two or more kinds of such oxy C₂₋₄alkylene units.

The polymer compound preferably contains a repeating structure of oxyC₂₋₄ alkylene units. The repeating structure may contain one kind of oxyC₂₋₄ alkylene unit, or may contain two or more kinds of oxy C₂₋₄alkylene units. The polymer compound may contain one kind of therepeating structure or two or more kinds of repeating structures.

Examples of the polymer compound include hydroxy compounds having arepeating structure of oxy C₂₋₄ alkylene units (poly C₂₋₄ alkyleneglycols, copolymers containing a repeating structure of oxy C₂₋₄alkylene, C₂₋₄ alkylene oxide adducts of a polyol, and the like),etherified or esterified products of these hydroxy compounds, and thelike.

Examples of the copolymer include copolymers containing different oxyC₂₋₄ alkylene units, poly C₂₋₄ alkylene glycol alkyl ethers, poly C₂₋₄alkylene glycol esters of carboxylic acids, and the like. The copolymermay be a block copolymer.

The polyol may be any of an aliphatic polyol, an alicyclic polyol, anaromatic polyol, a heterocyclic polyol, and the like. From the viewpointthat the polymer compound easily spreads thinly on the lead surface,aliphatic polyols, alicyclic polyols (for example,polyhydroxycyclohexane, polyhydroxynorbornane, and the like), and thelike are preferable, and among them, aliphatic polyols are preferable.Examples of the aliphatic polyol include aliphatic diols and polyols oftriol or higher (for example, glycerin, trimethylolpropane,pentaerythritol, sugar alcohol, and the like), and the like. Examples ofthe aliphatic diol include an alkylene glycol having 5 or more carbonatoms. The alkylene glycol may be, for example, a C₅₋₁₄ alkylene glycolor a C₅₋₁₀ alkylene glycol. Examples of the sugar alcohol includeerythritol, xylitol, mannitol, sorbitol, and the like. In the alkyleneoxide adduct of the polyol, the alkylene oxide corresponds to an oxyC₂₋₄ alkylene unit of the polymer compound and contains at least C₂₋₄alkylene oxide. From the viewpoint that the polymer compound easily takea linear structure, the polyol is preferably a diol.

The etherified product has an —OR² group obtained by etherifying —OHgroups (—OH groups composed of a hydrogen atom of a terminal group andan oxygen atom bonded to the hydrogen atom) at at least a part ofterminals of the hydroxy compound having the repeating structure of oxyC₂₋₄ alkylene units (wherein R² is an organic group). Among terminals ofthe polymer compound, some terminals may be etherified, or all terminalsmay be etherified. For example, one terminal of a main chain of thelinear polymer compound may be an —OH group, and the other terminal maybe an —OR² group.

The esterified product has an —O—C(═O)—R³ group obtained by esterifying—OH groups (—OH groups composed of a hydrogen atom of a terminal groupand an oxygen atom bonded to the hydrogen atom) at at least a part ofterminals of the hydroxy compound having the repeating structure of oxyC₂₋₄ alkylene units (wherein R³ is an organic group). Among terminals ofthe polymer compound, some terminals may be esterified, or all terminalsmay be esterified. For example, one terminal of a main chain of thelinear polymer compound may be an —OH group, and the other terminal maybe an —O—C(═O)—R³ group.

Examples of each of the organic groups R² and R³ include a hydrocarbongroup. The hydrocarbon group may have a substituent (for example, ahydroxy group, an alkoxy group, and/or a carboxy group, and the like).The hydrocarbon group may be any of aliphatic, alicyclic, and aromatic.The aromatic hydrocarbon group and the alicyclic hydrocarbon group mayhave an aliphatic hydrocarbon group (for example, an alkyl group, analkenyl group, an alkynyl group, or the like) as a substituent. Thenumber of carbon atoms of the aliphatic hydrocarbon group as asubstituent may be, for example, 1 to 20, 1 to 10, 1 to 6, or 1 to 4.

Examples of the aromatic hydrocarbon group include aromatic hydrocarbongroups having 24 or less carbon atoms (for example, 6 to 24). The numberof carbon atoms of the aromatic hydrocarbon group may be 20 or less (forexample, 6 to 20), 14 or less (for example, 6 to 14), or 12 or less (forexample, 6 to 12). Examples of the aromatic hydrocarbon group include anaryl group, a bisaryl group, and the like. Examples of the aryl groupinclude a phenyl group, a naphthyl group, and the like. Examples of thebisaryl group include monovalent groups corresponding to bisarene.Examples of the bisarene include biphenyl and bisarylalkanes (forexample, bis C₆₋₁₀ aryl C₁₋₄ alkanes (such as 2,2-bisphenylpropane), andthe like).

Examples of the alicyclic hydrocarbon group include alicyclichydrocarbon groups having 16 or less carbon atoms. The alicyclichydrocarbon group may be a bridged cyclic hydrocarbon group. The numberof carbon atoms of the alicyclic hydrocarbon group may be 10 or less or8 or less. The number of carbon atoms of the alicyclic hydrocarbon groupis, for example, 5 or more, and may be 6 or more.

The number of carbon atoms of the alicyclic hydrocarbon group may be 5(or 6) or more and 16 or less, 5 (or 6) or more and 10 or less, or 5 (or6) or more and 8 or less.

Examples of the alicyclic hydrocarbon group include cycloalkyl groups(cyclopentyl group, cyclohexyl group, cyclooctyl group, and the like),cycloalkenyl groups (cyclohexenyl group, cyclooctenyl group, and thelike), and the like. The alicyclic hydrocarbon group also includeshydrogenated products of the aromatic hydrocarbon groups.

Among the hydrocarbon groups, an aliphatic hydrocarbon group ispreferable from the viewpoint that the polymer compound easily adheresthinly to the lead surface. Examples of the aliphatic hydrocarbon groupinclude alkyl groups, alkenyl groups, alkynyl groups, dienyl groups, andthe like. The aliphatic hydrocarbon group may be either linear orbranched.

The number of carbon atoms of the aliphatic hydrocarbon group is, forexample, 30 or less, and may be 26 or less or 22 or less, 20 or less or16 or less, 14 or less or 10 or less, or 8 or less or 6 or less. Thelower limit of the number of carbon atoms is 1 or more for an alkylgroup, 2 or more for an alkenyl group and an alkynyl group, and 3 ormore for a dienyl group, depending on the type of the aliphatichydrocarbon group. Among them, an alkyl group and an alkenyl group arepreferable from the viewpoint that the polymer compound easily adheresthinly to the lead surface.

Specific examples of the alkyl group include methyl, ethyl, n-propyl,i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, neopentyl,i-pentyl, s-pentyl, 3-pentyl, t-pentyl, n-hexyl, 2-ethylhexyl, n-octyl,n-decyl, i-decyl, lauryl, myristyl, cetyl, stearyl, behenyl, and thelike.

Specific examples of the alkenyl group include vinyl, 1-propenyl, allyl,palmitoleyl, oleyl, and the like. An alkenyl group may be, for example,a C₂₋₃₀ alkenyl group or a C₂₋₂₆ alkenyl group, a C₂₋₂₂ alkenyl group ora C₂₋₂₀ alkenyl group, or a C₁₀₋₂₀ alkenyl group.

When an etherified product of a hydroxy compound having a repeatingstructure of oxy C₂₋₄ alkylene units and/or an esterified product of ahydroxy compound having a repeating structure of oxy C₂₋₄ alkylene unitsare used among the polymer compounds, it is preferable because theeffect of suppressing the deterioration of the charge acceptability canbe further enhanced. Even when these polymer compounds are used, a highliquid decrease suppressing effect can be secured.

The negative electrode material may contain one kind or two or morekinds of polymer compounds.

From the viewpoint of further enhancing the effect of reducing theamount of overcharge and enhancing the effect of suppressing thedeterioration of the charge acceptability and/or the low temperature HRdischarge performance, it is preferable that the repeating structure ofoxy C₂₋₄ alkylene includes at least a repeating structure ofoxypropylene units. The polymer compound containing the oxypropyleneunit has peaks derived from —CH< and —CH₂— of the oxypropylene unit in arange of 3.2 ppm to 3.8 ppm in a chemical shift of ¹H-NMR spectrum.Since electron densities around a nucleus of a hydrogen atom in thesegroups are different, the peak is split. Such a polymer compound haspeaks, for example, in a range of 3.2 ppm or more and 3.42 ppm or lessand a range of more than 3.42 ppm and 3.8 ppm or less in a chemicalshift of ¹H-NMR spectrum. The peak in the range of 3.2 ppm or more and3.42 ppm or less is derived from —CH₂—, and the peak in the range ofmore than 3.42 ppm and 3.8 ppm or less is derived from —CH< and —CH₂—.

Examples of such a polymer compound include polypropylene glycol, acopolymer containing a repeating structure of oxypropylene, a propyleneoxide adduct of the polyol, etherified or esterified products thereof,and the like. Examples of the copolymer include oxypropylene-oxyalkylenecopolymers (provided that the oxyalkylene is a C₂₋₄ alkylene other thanoxypropylene), polypropylene glycol alkyl ethers, a polypropylene glycolester of a carboxylic acid, and the like. Examples of theoxypropylene-oxyalkylene copolymer include an oxypropylene-oxyethylenecopolymer, an oxypropylene-oxytrimethylene copolymer, and the like. Theoxypropylene-oxyalkylene copolymer may be a block copolymer.

In the polymer compound containing a repeating structure ofoxypropylene, the proportion of the oxypropylene unit is, for example, 5mol % or more, and may be 10 mol % or more or 20 mol % or more.

It is preferable that the polymer compound contains a large amount ofoxy C₂₋₄ alkylene units from the viewpoint of enhancing adsorptivity tolead and easily taking a linear structure. Such a polymer compoundincludes, for example, an oxygen atom bonded to a terminal group and a—CH₂— group and/or a —CH< group bonded to the oxygen atom. In the ¹H-NMRspectrum of the polymer compound, the ratio of the integrated value ofthe peak of 3.2 ppm to 3.8 ppm to the sum of the integrated value ofthis peak, the integrated value of the peak of the hydrogen atoms of the—CH₂— group, and the integrated value of the peak of the hydrogen atomof the —CH< group increases. This ratio is, for example, 50% or more,and may be 80% or more. From the viewpoint of further enhancing theeffect of reducing the amount of overcharge and further enhancing theeffect of suppressing the deterioration of the charge acceptabilityand/or the low temperature HR discharge performance, the above ratio ispreferably 85% or more, and more preferably 90% or more. For example,when the polymer compound has an —OH group at a terminal and also has a—CH₂— group or a —CH< group bonded to an oxygen atom of the —OH group,in the ¹H-NMR spectrum, the peaks of the hydrogen atoms of the —CH₂—group and the —CH< group have a chemical shift in a range of more than3.8 ppm and 4.0 ppm or less.

The polymer compound may contain a compound having Mn of 500 or more, acompound having Mn of 600 or more, or a compound having Mn of 1,000 ormore. Mn of such a compound is, for example, 20,000 or less, and may be15,000 or less or 10,000 or less. The Mn of the compound is preferably5,000 or less and may be 4,000 or less or 3,000 or less, from theviewpoint of easily retaining the compound in the negative electrodematerial and easily spreading the compound thinner on the lead surface.

The Mn of the compound may be 500 or more (or 600 or more) and 20,000 orless, 500 or more (or 600 or more) and 15,000 or less, 500 or more (or600 or more) and 10,000 or less, 500 or more (or 600 or more) and 5,000or less, 500 or more (or 600 or more) and 4,000 or less, 500 or more (or600 or more) and 3,000 or less, 1,000 or more and 20,000 or less (or15,000 or less), 1,000 or more and 10,000 or less (or 5,000 or less), or1,000 or more and 4,000 or less (or 3,000 or less).

The polymer compound preferably contains at least a compound having Mnof 1,000 or more. Mn of such a compound may be 1,000 or more and 20,000or less, 1,000 or more and 15,000 or less, or 1,000 or more and 10,000or less. The Mn of the compound is preferably 1,000 or more and 5,000 orless, and may be 1,000 or more and 4,000 or less, or 1,000 or more and3,000 or less, from the viewpoint of easily retaining the compound inthe negative electrode material and easily spreading more thinly to thelead surface. When a compound having such Mn is used, the amount ofovercharge can be reduced more easily. By reducing the amount ofovercharge, the structural change of the negative active material due tocollision of the hydrogen gas with the negative active material can alsobe suppressed. Thus, the effect of suppressing the deterioration of thelow temperature HR discharge performance after the high temperaturelight load test can be enhanced. Since the compound having Mn asdescribed above easily moves into the negative electrode material evenwhen the compound is contained in the electrolyte solution, the compoundcan be replenished into the negative electrode material, and from such aviewpoint, the compound is easily retained in the negative electrodematerial. As the polymer compound, two or more compounds havingdifferent Mn may be used. That is, the polymer compound may have aplurality of peaks of Mn in the distribution of the molecular weight.

The content of the polymer compound in the negative electrode materialis, for example, more than 8 ppm, preferably 13 ppm or more, and morepreferably 15 ppm or more or 16 ppm or more on a mass basis. When thecontent of the polymer compound is in such a range, hydrogen generationvoltage can be more easily increased, and the effect of reducing theamount of overcharge can be further enhanced. From the viewpoint ofeasily securing higher low temperature HR discharge performance, thecontent (mass basis) of the polymer compound in the negative electrodematerial may be 50 ppm or more or 80 ppm or more. The content (massbasis) of the polymer compound in the negative electrode material is,for example, less than 400 ppm, preferably 360 ppm or less, and morepreferably 350 ppm or less. When the content of the polymer compound is400 ppm or less, the lead surface is suppressed from being excessivelycovered with the polymer compound, so that the deterioration of the lowtemperature HR discharge performance can be effectively suppressed. Fromthe viewpoint of easily securing higher low temperature HR dischargeperformance, the content (mass basis) of the polymer compound ispreferably 240 ppm or less, more preferably 200 ppm or less, and may be165 ppm or less or 164 ppm or less. These lower limit values and upperlimit values can be combined arbitrarily.

The content (mass basis) of the polymer compound may be more than 8 ppm(or 13 ppm or more) and less than 400 ppm, more than 8 ppm (or 13 ppm ormore) and 360 ppm or less, more than 8 ppm (or 13 ppm or more) and 350ppm or less, more than 8 ppm (or 13 ppm or more) and 240 ppm or less,more than 8 ppm (or 13 ppm or more) and 200 ppm or less, more than 8 ppm(or 13 ppm or more) and 165 ppm or less, more than 8 ppm (or 13 ppm ormore) and 164 ppm or less, 15 ppm or more (or 16 ppm or more) and lessthan 400 ppm, 15 ppm or more (or 16 ppm or more) and 360 ppm or less, 15ppm or more (or 16 ppm or more) and 350 ppm or less, 15 ppm or more (or16 ppm or more) and 240 ppm or less, 15 ppm or more (or 16 ppm or more)and 200 ppm or less, 15 ppm or more (or 16 ppm or more) and 165 ppm orless, 15 ppm or more (or 16 ppm or more) and 164 ppm or less, 50 ppm ormore (or 80 ppm or more) and less than 400 ppm, 50 ppm or more (or 80ppm or more) and 360 ppm or less, 50 ppm or more (or 80 ppm or more) and350 ppm or less, 50 ppm or more (or 80 ppm or more) and 240 ppm or less,50 ppm or more (or 80 ppm or more) and 200 ppm or less, 50 ppm or more(or 80 ppm or more) and 165 ppm or less, or 50 ppm or more (or 80 ppm ormore) and 164 ppm or less.

(Expander)

The negative electrode material can contain an expander. As theexpander, an organic expander is preferable. As the organic expander,lignins and/or a synthetic organic expander may be used. Examples of thelignins include lignin, lignin derivatives, and the like. Examples ofthe lignin derivative include lignin sulfonic acid or salts thereof(such as alkali metal salts (sodium salts and the like)), and the like.The organic expanders are generally roughly classified into lignins andsynthetic organic expanders. It can also be said that the syntheticorganic expander is an organic expander other than lignins. Thesynthetic organic expander is an organic polymer containing sulfurelement, and generally contains a plurality of aromatic rings in themolecule and sulfur element as a sulfur-containing group. Among thesulfur-containing groups, a sulfonic acid group or a sulfonyl groupwhich is in a stable form is preferable. The sulfonic acid group mayexist in an acid form, or may exist in a salt form like a Na salt. Thenegative electrode material may contain one kind or two or more kinds ofexpanders.

As the organic expander, it is preferable to use a condensate containingat least a unit of an aromatic compound. Examples of such a condensateinclude a condensate of an aromatic compound with an aldehyde compound(aldehydes (for example, formaldehyde) and/or condensates thereof, andthe like). The organic expander may contain a unit of one kind of anaromatic compound or a unit of two or more kinds of aromatic compounds.Note that the unit of an aromatic compound refers to a unit derived froman aromatic compound incorporated in a condensate.

As the organic expander, one synthesized by a known method may be used,or a commercially available product may be used. The condensatecontaining a unit of an aromatic compound is obtained, for example, byreacting an aromatic compound with an aldehyde compound. For example, byperforming this reaction in the presence of a sulfite or using anaromatic compound containing sulfur element (for example, bisphenol S orthe like), an organic expander containing sulfur element can beobtained. For example, the sulfur element content in the organicexpander can be adjusted by adjusting the amount of sulfite and/or theamount of the aromatic compound containing sulfur element. Also whenother raw materials are used, the condensate containing a unit of anaromatic compound can be obtained according to this method.

Examples of the aromatic ring of the aromatic compound include a benzenering, a naphthalene ring, and the like. When the aromatic compound has aplurality of aromatic rings, the plurality of aromatic rings may belinked by a direct bond, a linking group (for example, an alkylene group(including an alkylidene group), a sulfone group, and the like), or thelike. Examples of such a structure include bisarene structures(biphenyl, bisphenylalkane, bisphenylsulfone, and the like). Examples ofthe aromatic compound include compounds having the aromatic ring and ahydroxy group and/or an amino group. The hydroxy group or the aminogroup may be directly bonded to the aromatic ring, or may be bonded asan alkyl chain having a hydroxy group or an amino group. Note that thehydroxy group also includes salts of hydroxy group (—OMe). The aminogroup also includes salts of amino group (salts with anion). Examples ofMe include alkali metals (Li, K, Na, and the like), Group 2 metals ofthe periodic table (Ca, Mg, and the like), and the like.

As the aromatic compound, bisarene compounds [bisphenol compounds,hydroxybiphenyl compounds, bisarene compounds having an amino group(bisarylalkane compounds having an amino group, bisarylsulfone compoundshaving an amino group, biphenyl compounds having an amino group, and thelike), hydroxyarene compounds (hydroxynaphthalene compounds, phenolcompounds, and the like), aminoarene compounds (aminonaphthalenecompounds, aniline compounds (aminobenzenesulfonic acid,alkylaminobenzenesulfonic acid, and the like), and the like), and thelike] are preferable. The aromatic compound may further have asubstituent. The organic expander may contain one or more or a pluralityof residues of these compounds. As the bisphenol compound, bisphenol A,bisphenol S, bisphenol F, and the like are preferable.

The condensate preferably contains a unit of an aromatic compound havingat least a sulfur-containing group. In particular, when a condensatecontaining at least a unit of a bisphenol compound having asulfur-containing group is used, an effect of suppressing deteriorationof low temperature HR discharge performance after high temperature lightload test can be enhanced. Without limiting to this case, a condensateof a naphthalene compound having a sulfur-containing group and having ahydroxy group and/or an amino group with an aldehyde compound may beused.

The sulfur-containing group may be directly bonded to the aromatic ringcontained in the compound, and for example, may be bonded to thearomatic ring as an alkyl chain having a sulfur-containing group. Thesulfur-containing group is not particularly limited, and examplesthereof include a sulfonyl group, a sulfonic acid group or a saltthereof, and the like.

In addition, as the organic expander, for example, at least a condensatecontaining at least one selected from the group consisting of units ofthe bisarene compound and units of a monocyclic aromatic compound(hydroxyarene compound and/or aminoarene compound, or the like) may beused. The organic expander may contain at least a condensate containinga unit of a bisarene compound and a unit of a monocyclic aromaticcompound (among them, hydroxyarene compound). Examples of such acondensate include a condensate of a bisarene compound and a monocyclicaromatic compound with an aldehyde compound. As the hydroxyarenecompound, a phenol sulfonic acid compound (phenol sulfonic acid, asubstituted product thereof, or the like) is preferable. As theaminoarene compound, aminobenzenesulfonic acid,alkylaminobenzenesulfonic acid, and the like are preferable. As themonocyclic aromatic compound, a hydroxyarene compound is preferable.

The negative electrode material may contain, for example, the firstorganic expander having a sulfur element content of 2,000 μmol/g or moreamong the organic expanders. Examples of the first organic expanderinclude the synthetic organic expander describe above (such as thecondensate).

The sulfur element content of the first organic expander may be 2,000μmol/g or more, and is preferably 3,000 μmol/g or more. The upper limitof the sulfur element content of the organic expander is notparticularly limited, and is preferably 9,000 μmol/g or less, and morepreferably 8,000 μmol/g or less or 7,000 μmol/g or less from theviewpoint of enhancing an effect of suppressing the liquid decrease.These lower limit values and upper limit values can be combinedarbitrarily. By combining such an organic expander and the polymercompound, the dissolution of lead sulfate during charge is less likelyto be inhibited, so that the deterioration of the charge acceptabilitycan be suppressed.

The sulfur element content of the first organic expander may be, forexample, 2,000 μmol/g or more (or 3,000 μmol/g or more) and 9,000 μmol/gor less, 2,000 μmol/g or more (or 3,000 μmol/g or more) and 8,000 μmol/gor less, or 2,000 μmol/g or more (or 3,000 μmol/g or more) and 7,000μmol/g or less.

A weight average molecular weight (Mw) of the first organic expander ispreferably, for example, 7,000 or more. The Mw of the first organicexpander is, for example, 100,000 or less, and may be 20,000 or less.

In the present specification, the Mw of the organic expander isdetermined by GPC. A standard substance used for determining the Mw issodium polystyrene sulfonate.

The Mw is measured under the following conditions using the followingapparatus.

GPC apparatus: Build-up GPC systemSD-8022/DP-8020/AS-8020/CO-8020/UV-8020 (manufactured by TosohCorporation)

Column: TSKgel G4000SWXL, G2000SWXL (7.8 mm I.D.×30 cm) (manufactured byTosoh Corporation)

Detector: UV detector, A=210 nm Eluent: Mixed solution of NaCl aqueoussolution having a concentration of 1 mol/L: acetonitrile (volumeratio=7:3)

Flow rate: 1 mL/min.

Concentration: 10 mg/mL

Injection amount: 10 μL

Standard substance: Na polystyrene sulfonate (Mw=275,000, 35,000,12,500, 7,500, 5,200, 1,680)

The negative electrode material can contain, for example, the secondorganic expander having a sulfur element content of less than 2,000μmol/g. Examples of the second organic expander include lignins andsynthetic organic expanders (in particular, lignins) among the organicexpanders described above. The sulfur element content of the secondorganic expander is preferably 1,000 μmol/g or less, and may be 800μmol/g or less. The lower limit of the sulfur element content in thesecond organic expander is not particularly limited, and is, forexample, 400 μmol/g or more. When the second organic expander and thepolymer compound are used in combination, the particle size of thecolloid can be reduced, so that the effect of suppressing thedeterioration of the low temperature HR discharge performance can befurther enhanced.

The Mw of the second organic expander is, for example, less than 7,000.The Mw of the second organic expander is, for example, 3,000 or more.

When the first organic expander and the second organic expander are usedin combination, the mass ratio thereof can be arbitrarily selected. Fromthe viewpoint of easily securing the synergistic effect in suppressingthe deterioration of the charge acceptability, a ratio of the firstorganic expander to a total amount of the first organic expander and thesecond organic expander is preferably 20% by mass or more, and may be25% by mass or more. From the same viewpoint, the ratio of the firstorganic expander to the total amount of the first organic expander andthe second organic expander is preferably 80% by mass or less, and maybe 75% by mass or less.

The ratio of the first organic expander to the total amount of the firstorganic expander and the second organic expander may be 20% by mass ormore and 80% by mass or less (or 75% by mass or less), or 25% by mass ormore and 80% by mass or less (or 75% by mass or less).

The content of the organic expander contained in the negative electrodematerial is, for example, 0.01% by mass or more and may be 0.05% by massor more. The content of the organic expander is, for example, 1.0% bymass or less and may be 0.5% by mass or less. These lower limit valuesand upper limit values can be combined arbitrarily.

The content of the organic expander contained in the negative electrodematerial may be 0.01% by mass or more and 1.0% by mass or less, 0.05% bymass or more and 1.0% by mass or less, 0.01% by mass or more and 0.5% bymass or less, or 0.05% by mass or more and 0.5% by mass or less.

(Carbonaceous Material)

As the carbonaceous material contained in the negative electrodematerial, carbon black, graphite, hard carbon, soft carbon, and the likecan be used. Examples of the carbon black include acetylene black,Ketjen black, furnace black, lamp black, and the like. The graphite maybe a carbonaceous material including a graphite-type crystal structureand may be either artificial graphite or natural graphite. One kind ofcarbonaceous material may be used alone, or two or more kinds thereofmay be used in combination.

The content of the carbonaceous material in the negative electrodematerial is, for example, 0.05% by mass or more and may be 0.10% by massor more. The content of the carbonaceous material is, for example, 5% bymass or less and may be 3% by mass or less. These lower limit values andupper limit values can be combined arbitrarily.

The content of the carbonaceous material in the negative electrodematerial may be 0.05% by mass or more and 5% by mass or less, 0.05% bymass or more and 3% by mass or less, 0.10% by mass or more and 5% bymass or less, or 0.10% by mass or more and 3% by mass or less.

(Barium Sulfate)

The content of barium sulfate in the negative electrode material is, forexample, 0.05% by mass or more and may be 0.10% by mass or more. Thecontent of barium sulfate in the negative electrode material is 3% bymass or less and may be 2% by mass or less. These lower limit values andupper limit values can be combined arbitrarily.

The content of barium sulfate in the negative electrode material may be0.05% by mass or more and 3% by mass or less, 0.05% by mass or more and2% by mass or less, 0.10% by mass or more and 3% by mass or less, or0.10% by mass or more and 2% by mass or less.

(Analysis of Constituent Components of Negative Electrode Material)

Hereinafter, a method of analyzing the negative electrode material orconstituent components thereof will be described. Prior to analysis, alead-acid battery after formation is fully charged and then disassembledto obtain a negative electrode plate to be analyzed. The obtainednegative electrode plate is washed with water to remove sulfuric acidfrom the negative electrode plate. The washing with water is performeduntil it is confirmed that color of a pH test paper does not change bypressing the pH test paper against the surface of the negative electrodeplate washed with water. However, the washing with water is performedwithin two hours. The negative electrode plate washed with water isdried at 60±5° C. in a reduced pressure environment for about six hours.When an attached member is included after drying, the attached member isremoved from the negative electrode plate by peeling. Next, the negativeelectrode material is separated from the negative electrode plate toobtain a sample (hereinafter referred to as sample A). Sample A isground as necessary and subjected to analysis.

(1) Analysis of Polymer Compound (1-1) Qualitative Analysis of PolymerCompound

150.0±0.1 mL of chloroform is added to 100.0±0.1 g of the pulverizedsample A, and the mixture is stirred at 20±5° C. for 16 hours to extracta polymer compound. Thereafter, the solid content is removed byfiltration. For a chloroform solution in which the polymer compoundobtained by the extraction is dissolved or a polymer compound obtainedby drying the chloroform solution, information is obtained from aninfrared spectroscopic spectrum, an ultraviolet-visible absorptionspectrum, an NMR spectrum, LC-MS and/or pyrolysis GC-MS, and the like tospecify the polymer compound.

Chloroform is distilled off under reduced pressure from the chloroformsolution in which the polymer compound obtained by the extraction isdissolved to recover a chloroform soluble component. The chloroformsoluble component is dissolved in deuterated chloroform, and a ¹H-NMRspectrum is measured under the following conditions. From this ¹H-NMRspectrum, a peak with a chemical shift in the range of 3.2 ppm or moreand 3.8 ppm or less is confirmed. Also, from the peak in this range, thetype of the oxy C₂₋₄ alkylene unit is specified.

Apparatus: type AL400 nuclear magnetic resonance spectrometer,manufactured by JEOL Ltd.

Observation frequency: 395.88 MHz

Pulse width: 6.30 μs

Pulse repeating time: 74.1411 seconds

Number of integrations: 32

Measurement temperature: room temperature (20 to 35° C.)

Reference: 7.24 ppm

Sample tube diameter: 5 mm

From the ¹H-NMR spectrum, an integrated value (V₁) of the peak at whichthe chemical shift is present in the range of 3.2 ppm or more and 3.8ppm or less is determined. In addition, for each of the hydrogen atomsof the —CH₂— group and the —CH< group bonded to the oxygen atom bondedto the terminal group of the polymer compound, the sum (V₂) ofintegrated values of peaks in the ¹H-NMR spectrum is determined. Then,from V₁ and V₂, a ratio of V₁ to the sum of V₁ and V₂(=V₁/(V₁+V₂)×100(%)) is determined.

When the integrated value of the peak in the ¹H-NMR spectrum isdetermined in the qualitative analysis, two points having no significantsignal are determined so as to sandwich the corresponding peak in the¹H-NMR spectrum, and each integrated value is calculated using astraight line connecting the two points as a baseline. For example, forthe peak in which the chemical shift is present in a range of 3.2 ppm to3.8 ppm, a straight line connecting two points of 3.2 ppm and 3.8 ppm inthe spectrum is used as a baseline. For example, for a peak in which thechemical shift is present in a range of more than 3.8 ppm and 4.0 ppm orless, a straight line connecting two points of 3.8 ppm and 4.0 ppm inthe spectrum is used as a baseline.

(1-2) Quantitative Analysis of Polymer Compound

An appropriate amount of the chloroform soluble component is dissolvedin deuterated chloroform together with tetrachloroethane (TCE) of m_(r)(g) measured with an accuracy of ±0.0001 g, and a ¹H-NMR spectrum ismeasured. An integrated value (S_(a)) of the peak in which the chemicalshift is present in the range of 3.2 to 3.8 ppm and an integrated value(S_(r)) of a peak derived from TCE are determined, and mass-basedcontent C_(n) (ppm) of the polymer compound in the negative electrodematerial is determined from the following formula.

C _(n) =S _(a) /S _(r) ×N _(r) /N _(a) ×M _(a) /M _(r) ×m _(r)/m×1,000,000

(wherein M_(a) is a molecular weight of a structure showing a peak in achemical shift range of 3.2 to 3.8 ppm (more specifically, a molecularweight of the repeating structure of oxy C₂₋₄ alkylene units), and N_(a)is the number of hydrogen atoms bonded to a carbon atom of a main chainof the repeating structure. N_(r) and M_(r) are the number of hydrogencontained in a molecule of reference substance and the molecular weightof the reference substance, respectively, and m (g) is the mass of thenegative electrode material used for extraction.)

Since the reference substance in this analysis is TCE, N_(r)=2 andM_(r)=168. In addition, m=100.

For example, when the polymer compound is polypropylene glycol, M_(a) is58, and N_(a) is 3. When the polymer compound is polyethylene glycol,M_(a) is 44, and N_(a) is 4. In the case of a copolymer, N_(a) is avalue obtained by averaging N_(a) values of each monomer unit using amolar ratio (mol %) of each monomer unit contained in the repeatingstructure, and M_(a) is determined according to the type of each monomerunit.

In the quantitative analysis, the integrated value of the peak in the¹H-NMR spectrum is determined using data processing software “ALICE”manufactured by JEOL Ltd.

(1-3) Mn Measurement of Polymer Compound

GPC Measurement of the polymer compound is performed using the followingapparatus under the following conditions. Separately, a calibrationcurve (standard curve) is prepared from a plot of Mn of the standardsubstance and elution time. The Mn of the polymer compound is calculatedbased on the standard curve and the GPC measurement result of thepolymer compound.

Analysis system: 20A system (manufactured by Shimadzu Corporation)

Column: two columns of GPC KF-805L (manufactured by Shodex) connected inseries

Column temperature: 30° C.

Mobile phase: tetrahydrofuran

Flow rate: 1 mL/min.

Concentration: 0.20% by mass

Injection amount: 10 μL

Standard substance: polyethylene glycol (Mn=2,000,000, 200,000, 20,000,2,000, 200)

Detector: differential refractive index detector (Shodex RI-201H,manufactured by Shodex)

(2) Analysis of Organic Expander (2-1) Qualitative Analysis of OrganicExpander in Negative Electrode Material

Sample A is immersed in a 1 mol/L sodium hydroxide (NaOH) aqueoussolution to extract the organic expander. Next, the first organicexpander and the second organic expander are separated from the extract.For each separated material containing each organic expander, insolublecomponents are removed by filtration, and the obtained solution isdesalted, then concentrated, and dried. The desalination is performed byusing a desalination column, by causing the solution to pass through anion-exchange membrane, or by placing the solution in a dialysis tube andimmersing the solution in distilled water. The solution is dried toobtain a powder sample (hereinafter, also referred to as a powder sampleB) of the organic expander.

A type of the organic expander is specified using a combination ofinformation obtained from an infrared spectroscopic spectrum measuredusing the powder sample of the organic expander obtained as describedabove, an ultraviolet-visible absorption spectrum measured by anultraviolet-visible absorption spectrometer after the powder sample isdiluted with distilled water or the like, an NMR spectrum of a solutionobtained by dissolution with a predetermined solvent such as heavywater, and the like.

The first organic expander and the second organic expander are separatedfrom the extract as follows. First, the extract is measured by infraredspectroscopy, NMR, and/or GC-MS to determine whether or not a pluralityof types of organic expanders are contained. Next, a molecular weightdistribution is measured by GPC analysis of the extract, and if theplurality of types of organic expanders can be separated by molecularweight, the organic expander is separated by column chromatography basedon a difference in molecular weight. When it is difficult to separatethe organic expander due to the difference in molecular weight, one ofthe organic expanders is separated by a precipitation separation methodusing a difference in solubility that varies depending on the type ofthe functional group and/or the amount of the functional group of theorganic expander. Specifically, an aqueous sulfuric acid solution isadded dropwise to a mixture obtained by dissolving the extract in anNaOH aqueous solution to adjust the pH of the mixture, therebyaggregating and separating one of the organic expanders. The insolublecomponent is removed by filtration as described above from the separatedmaterial dissolved again in the NaOH aqueous solution. The remainingsolution after separating one of the organic expanders is concentrated.The obtained concentrate contains the other organic expander, and theinsoluble component is removed from the concentrate by filtration asdescribed above.

(2-2) Quantitative Determination of Content of Organic Expander inNegative Electrode Material

Similarly to (2-1) above, for each separated material containing theorganic expander, a solution is obtained after removing the insolublecomponent by filtration. The ultraviolet-visible absorption spectrum ofeach obtained solution is measured. The content of each organic expanderin the negative electrode material is determined using an intensity of acharacteristic peak of each organic expander and a calibration curveprepared in advance.

When a lead-acid battery in which the content of the organic expander isunknown is obtained and the content of the organic expander is measured,a structural formula of the organic expander cannot be strictlyspecified, so that the same organic expander may not be used for thecalibration curve. In this case, the content of the organic expander ismeasured using the ultraviolet-visible absorption spectrum by creating acalibration curve using the organic expander extracted from the negativeelectrode of the battery and a separately available organic polymer inwhich the ultraviolet-visible absorption spectrum, the infraredspectroscopic spectrum, the NMR spectrum, and the like exhibit similarshapes.

(2-3) Content of Sulfur Element in Organic Expander

Similarly to (2-1) above, after a powder sample of the organic expanderis obtained, sulfur element in 0.1 g of the organic expander isconverted into sulfuric acid by an oxygen combustion flask method. Atthis time, the powder sample is burned in a flask containing anadsorbent to obtain an eluate in which sulfate ions are dissolved in theadsorbent. Next, the eluate is titrated with barium perchlorate usingthorin as an indicator to determine the content (C1) of the sulfurelement in 0.1 g of the organic expander. Next, C1 is multiplied by 10to calculate the content (μmol/g) of the sulfur element in the organicexpander per 1 g.

(3) Quantitative Determination of Carbonaceous Material and BariumSulfate

The uncrushed sample A is crushed, 50 ml of nitric acid having aconcentration of 20% by mass is added to 10 g of the crushed sample A,and the mixture is heated for about 20 minutes to dissolve a leadcomponent as lead nitrate. Next, a solution containing lead nitrate isfiltered, and solids such as carbonaceous materials and barium sulfateare filtered off.

The obtained solid is dispersed in water to form a dispersion, and thencomponents except for the carbonaceous material and barium sulfate(e.g., reinforcing material) are removed from the dispersion by using asieve. Next, the dispersion is subjected to suction filtration using amembrane filter with its mass measured in advance, and the membranefilter is dried with the filtered sample in a dryer at 110° C.±5° C. Thefiltered sample is a mixed sample of the carbonaceous material andbarium sulfate. A mass (M_(m)) of the mixed sample is measured bysubtracting the mass of the membrane filter from the total mass of driedmixed sample and the membrane filter. Thereafter, the dried mixed sampleis placed in a crucible together with a membrane filter and is burnedand incinerated at 700° C. or higher. The residue remaining is bariumoxide. The mass (MB) of barium sulfate is determined by converting themass of barium oxide to the mass of barium sulfate. The mass of thecarbonaceous material is calculated by subtracting the mass MB from themass M_(m).

(Others)

The negative electrode plate can be formed in such a manner that anegative current collector is coated or filled with a negative electrodepaste, which is then cured and dried to prepare a non-formed negativeelectrode plate, and thereafter, the non-formed negative electrode plateis formed. The negative electrode paste is prepared by adding water andsulfuric acid to lead powder and an organic expander, and variousadditives as necessary, and kneading the mixture. At the time of curing,it is preferable to cure the non-formed negative electrode plate at ahigher temperature than room temperature and high humidity.

The formation can be performed by charging the element in a state wherethe element including the non-formed negative electrode plate immersedin the electrolyte solution containing sulfuric acid in the container ofthe lead-acid battery. However, the formation may be performed beforethe lead-acid battery or the element is assembled. The formationproduces spongy lead.

(Positive Electrode Plate)

The positive electrode plate of a lead-acid battery can be classifiedinto a paste type, a clad type, and the like. The paste-type positiveelectrode plate includes a positive current collector and a positiveelectrode material. The positive electrode material is held by thepositive current collector. In the paste-type positive electrode plate,the positive electrode material is obtained by removing the positivecurrent collector from the positive electrode plate. The positivecurrent collector may be formed by casting lead (Pb) or a lead alloy, ormay be formed by processing a lead sheet or a lead alloy sheet. Examplesof the processing method include expanding processing and punchingprocessing. It is preferable to use a grid-like current collector as thepositive current collector because the positive electrode material iseasily supported. The clad-type positive electrode plate includes aplurality of porous tubes, a spine inserted into each tube, a currentcollector coupling the plurality of spines, a positive electrodematerial with which a spine inserted tube is filled, and a joint thatcouples the plurality of tubes. In the clad-type positive electrodeplate, the positive electrode material is a material obtained byremoving the tube, the spine, the current collector, and the joint. Inthe clad-type positive electrode plate, the spine and the currentcollector may be collectively referred to as a positive currentcollector.

A member such as a mat or a pasting paper may be stuck to the positiveelectrode plate. Such a member (sticking member) is used integrally withthe positive electrode plate and is thus assumed to be included in thepositive electrode plate. Also, when the positive electrode plateincludes such a member, the positive electrode material is obtained byremoving the positive current collector and the sticking member from thepositive electrode plate in the paste-type positive electrode plate.

As a lead alloy used for the positive current collector, a Pb—Sb alloy,a Pb—Ca alloy, or a Pb—Ca—Sn alloy are preferred in terms of corrosionresistance and mechanical strength. The positive current collector mayinclude a surface layer. The surface layer and the inner layer of thepositive current collector may have different compositions. The surfacelayer may be formed in a part of the positive current collector. Thesurface layer may be formed only on the grid portion, only on the lugportion, or only on the frame rib portion of the positive currentcollector.

The positive electrode material contained in the positive electrodeplate contains a positive active material (lead dioxide or lead sulfate)that exhibits a capacity through a redox reaction. The positiveelectrode material may optionally contain another additive.

A non-formed paste-type positive electrode plate is obtained by fillinga positive current collector with a positive electrode paste, and curingand drying the paste. The positive electrode paste is prepared bykneading lead powder, an additive, water, and sulfuric acid. Anon-formed clad-type positive electrode plate is formed by filling aporous tube, into which a spine connected by a current collector isinserted with lead powder or a slurry-like lead powder, and joining aplurality of tubes with a joint. Thereafter, the positive electrodeplate is obtained by forming the non-formed positive electrode plates.The formation can be performed by charging the element in a state wherethe element including the non-formed positive electrode plate immersedin the electrolyte solution containing sulfuric acid in the container ofthe lead-acid battery. However, the formation may be performed beforethe lead-acid battery or the element is assembled.

The formation can be performed by charging the element in a state wherethe element including the non-formed positive electrode plate immersedin the electrolyte solution containing sulfuric acid in the container ofthe lead-acid battery. However, the formation may be performed beforethe lead-acid battery or the element is assembled.

(Separator)

The separator can be disposed between the negative electrode plate andthe positive electrode plate. As the separator, a nonwoven fabric, amicroporous membrane, and/or the like are used. The thickness and thenumber of the separators interposed between the negative electrode plateand the positive electrode plate may be selected in accordance with thedistance between the electrodes.

The nonwoven fabric is a mat in which fibers are intertwined withoutbeing woven and is mainly made of fibers. In the nonwoven fabric, forexample, 60% by mass or more of the nonwoven fabric is formed of fibers.As the fibers, there can be used glass fibers, polymer fibers(polyolefin fiber, acrylic fiber, polyester fiber such as polyethyleneterephthalate fiber, etc.), pulp fibers, and the like. Among them, glassfibers are preferable. The nonwoven fabric may contain components inaddition to the fibers, such as acid-resistant inorganic powder, apolymer as a binder, and the like.

On the other hand, the microporous film is a porous sheet mainly made ofcomponents except for fiber components and is obtained by, for example,extrusion molding a composition containing, for example, a pore-formingadditive (polymer powder, oil, and/or the like) into a sheet shape andthen removing the pore-forming additive to form pores. The microporousfilm is preferably made of a material having acid resistance and ispreferably composed mainly of a polymer component. As the polymercomponent, a polyolefin such as polyethylene or polypropylene ispreferable.

The separator may be, for example, made of only a nonwoven fabric ormade of only a microporous film. The separator may be, when required, alaminate of a nonwoven fabric and a microporous film, a laminate ofdifferent or the same kind of materials, or a laminate of different orthe same kind of materials in which recesses and projections are engagedto each other.

The separator may have a sheet shape or may be formed in a bag shape.One sheet-like separator may be disposed between the positive electrodeplate and the negative electrode plate. Further, the electrode plate maybe disposed so as to be sandwiched by one sheet-like separator in afolded state. In this case, the positive electrode plate sandwiched bythe folded sheet-like separator and the negative electrode platesandwiched by the folded sheet-like separator may be overlapped, or oneof the positive electrode plate and the negative electrode plate may besandwiched by the folded sheet-like separator and overlapped with theother electrode plate. Also, the sheet-like separator may be folded intoa bellows shape, and the positive electrode plate and the negativeelectrode plate may be sandwiched by the bellows-shaped separator suchthat the separator is interposed therebetween. When the separator foldedin a bellows shape is used, the separator may be disposed such that thefolded portion is along the horizontal direction of the lead-acidbattery (e.g., such that the bent portion may be parallel to thehorizontal direction), and the separator may be disposed such that thefolded portion is along the vertical direction (e.g., such that the bentportion is parallel to the vertical direction). In the separator foldedin the bellows shape, recesses are alternately formed on both mainsurface sides of the separator. Since the lugs are usually formed on theupper portion of the positive electrode plate and the negative electrodeplate, when the separator is disposed such that the folded portions arealong the horizontal direction of the lead-acid battery, the positiveelectrode plate and the negative electrode plate are each disposed onlyin the recess on one main surface side of the separator (i.e., a doubleseparator is interposed between the adjacent positive and negativeplates). When the separator is disposed such that the folded portion isalong the vertical direction of the lead-acid battery, the positiveelectrode plate can be housed in the recess on one main surface side,and the negative electrode plate can be housed in the recess on theother main surface side (i.e., the separator can be interposed singlybetween the adjacent positive and negative plates). When the bag-shapedseparator is used, the bag-shaped separator may house the positiveelectrode plate or may house the negative electrode plate.

In the present specification, the up-down direction of the plate meansthe up-down direction of the lead-acid battery in the verticaldirection.

(Electrolyte Solution)

The electrolyte solution is an aqueous solution containing sulfuric acidand may be gelled as necessary.

The polymer compound may be contained in the electrolyte solution.

The concentration of the polymer compound in the electrolyte solutionmay be, for example, 500 ppm or less, 300 ppm or less, or 200 ppm orless on a mass basis. As described above, even when the amount of thepolymer compound contained in the electrolyte solution is small, theamount of overcharge can be reduced, and the deterioration of the chargeacceptability and the low temperature HR discharge performance can besuppressed. The concentration of the polymer compound in the electrolytesolution may be 1 ppm or more or 5 ppm or more on a mass basis. Theseupper limit values and lower limit values can be combined arbitrarily.

The concentration of the polymer compound in the electrolyte solutionmay be 1 ppm or more and 500 ppm or less, 1 ppm or more and 300 ppm orless, 1 ppm or more and 200 ppm or less, 5 ppm or more and 500 ppm orless, 5 ppm or more and 300 ppm or less, or 5 ppm or more and 200 ppm orless on a mass basis.

The concentration of the polymer compound in the electrolyte solutionmay be, for example, 100 ppm or more, may be 200 ppm or more or 500 ppmor more, may be more than 500 ppm, or may be 600 ppm or more on a massbasis. The polymer compound preferably contains at least a compoundhaving Mn of 1,000 or more and 5,000 or less (for example, 4,000 or lessor 3,000 or less). When the polymer compound is contained in thenegative electrode material and the electrolyte solution contains someconcentration of polymer compound, elution of the polymer compound fromthe negative electrode plate can be suppressed, and the polymer compoundcan be replenished from the electrolyte solution to the negativeelectrode plate.

The concentration of the polymer compound in the electrolyte solutionmay be, for example, 5,000 ppm or less, 4,000 ppm or less, 3,000 ppm orless, 2,500 ppm or less, or 2,400 ppm or less on a mass basis.

The concentration of the polymer compound in the electrolyte solutionmay be, on a mass basis, 100 ppm or more (or 200 ppm or more) and 5,000ppm or less, 100 ppm or more (or 200 ppm or more) and 4,000 ppm or less,100 ppm or more (or 200 ppm or more) and 3,000 ppm or less, 100 ppm ormore (or 200 ppm or more) and 2,500 ppm or less, 100 ppm or more (or 200ppm or more) and 2400 ppm or less, 500 ppm or more (or more than 500ppm) and 5,000 ppm or less, 500 ppm or more (or more than 500 ppm) and4,000 ppm or less, 500 ppm or more (or more than 500 ppm) and 3,000 ppmor less, 500 ppm or more (or more than 500 ppm) and 2,500 ppm or less,500 ppm or more (or more than 500 ppm) and 2,400 ppm or less, 600 ppm ormore and 5,000 ppm or less (or 4,000 ppm or less), 600 ppm or more and3,000 ppm or less (or 2,500 ppm or less), or 600 ppm or more and 2,400ppm or less.

Regarding the concentration of the polymer compound in the electrolytesolution, chloroform is added to and mixed with a predetermined amount(m₁ (g)) of the electrolyte solution taken out from the formed lead-acidbattery in a fully charged state, the mixture is allowed to stand to beseparated into two layers, and then only the chloroform layer is takenout. After repeating this operation several times, chloroform isdistilled off under reduced pressure to obtain a chloroform solublecontent. An appropriate amount of the chloroform soluble component isdissolved in deuterated chloroform together with 0.0212±0.0001 g of TCE,and a ¹H-NMR spectrum is measured. An integrated value (S_(a)) of thepeak in which the chemical shift is present in the range of 3.2 to 3.8ppm and an integrated value (S_(r)) of a peak derived from TCE aredetermined, and content C_(e) of the polymer compound in the electrolytesolution is determined from the following formula.

C _(e) =S _(a) /S _(r) ×N _(r) /N _(a) ×M _(a) /M _(r) ×m _(r) /m₁×1,000,000

wherein M_(a) and N_(a) are the same as described above.

The electrolyte solution may contain cations (e.g., metal cations suchas sodium ion, lithium ion, magnesium ion, and/or aluminum ion) and/oranions (e.g., anions other than sulfate anions such as phosphate ions)as necessary.

The specific gravity of the electrolyte solution in the lead-acidbattery in the fully charged state at 20° C. is, for example, 1.20 ormore and may be 1.25 or more. The specific gravity of the electrolytesolution at 20° C. is 1.35 or less and preferably 1.32 or less. Theselower limit values and upper limit values can be combined arbitrarily.The specific gravity of the electrolyte solution at 20° C. may be 1.20or more and 1.35 or less, 1.20 or more and 1.32 or less, 1.25 or moreand 1.35 or less, or 1.25 or more and 1.32 or less.

The lead-acid battery can be obtained by a production method including astep of assembling a lead-acid battery by housing a positive electrodeplate, a negative electrode plate, and an electrolyte solution in acontainer. In the assembly process of the lead-acid battery, theseparator is usually disposed so as to be interposed between thepositive electrode plate and the negative electrode plate. The assemblyprocess of the lead-acid battery may include a step of forming thepositive electrode plate and/or the negative electrode plate asnecessary after the step of housing the positive electrode plate, thenegative electrode plate, and the electrolyte solution in the container.The positive electrode plate, the negative electrode plate, theelectrolyte solution, and the separator are each prepared before beinghoused in the container.

FIG. 1 shows an appearance of an example of a lead-acid batteryaccording to an embodiment of the present invention. A lead-acid battery1 includes a container 12 that houses an element 11 and an electrolytesolution (not shown). The inside of the container 12 is partitioned bypartitions 13 into a plurality of cell chambers 14. Each of the cellchambers 14 contains one element 11. An opening of the container 12 isclosed with a lid 15 having a negative electrode terminal 16 and apositive electrode terminal 17. The lid 15 is provided with a vent plug18 for each cell chamber. At the time of water addition, the vent plug18 is removed to supply a water addition liquid. The vent plug 18 mayhave a function of discharging gas generated in the cell chamber 14 tothe outside of the battery.

The element 11 is configured by laminating a plurality of negativeelectrode plates 2 and positive electrode plates 3 with a separator 4interposed therebetween. Here, the bag-shaped separator 4 housing thenegative electrode plate 2 is shown, but the form of the separator isnot particularly limited. In the cell chamber 14 located at one end ofthe container 12, a negative electrode shelf portion 6 for connectingthe plurality of negative electrode plates 2 in parallel is connected toa penetrating connection body 8, and a positive electrode shelf portion5 for connecting the plurality of positive electrode plates 3 inparallel is connected to a positive pole 7. The positive pole 7 isconnected to the positive electrode terminal 17 outside the lid 15. Inthe cell chamber 14 located at the other end of the container 12, anegative pole 9 is connected to the negative electrode shelf portion 6,and the penetrating connection body 8 is connected to the positiveelectrode shelf portion 5. The negative pole 9 is connected to thenegative electrode terminal 16 outside the lid 15. Each of thepenetrating connection bodies 8 passes through a through-hole providedin the partition 13 to connect the elements 11 of the adjacent cellchambers 14 in series.

The positive electrode shelf portion 5 is formed by welding the lugs,provided on the upper portions of the respective positive electrodeplates 3, to each other by a cast-on-strap method or a burning method.The negative electrode shelf portion 6 is also formed by welding thelugs, provided on the upper portions of the respective negativeelectrode plates 2, to each other in accordance with the case of thepositive electrode shelf portion 5.

The lid 15 of the lead-acid battery has a single structure (single lid),but is not limited to the illustrated examples. The lid 15 may have, forexample, a double structure including an inner lid and an outer lid (oran upper lid). The lid having the double structure may have a refluxstructure between the inner lid and the outer lid for returning theelectrolyte solution into the battery (inside the inner lid) through areflux port provided in the inner lid.

The lead-acid battery according to one aspect of the present inventionwill be described below.

(1) A lead-acid battery including a positive electrode plate, a negativeelectrode plate, and an electrolyte solution,

in which the negative electrode plate includes a negative electrodematerial,

the negative electrode material contains a polymer compound, and

the polymer compound has a peak in a range of 3.2 ppm or more and 3.8ppm or less in a chemical shift of ¹H-NMR spectrum.

(2) In (1) above, the polymer compound may contain an oxygen atom bondedto a terminal group and a —CH₂— group and/or a —CH< group bonded to theoxygen atom, and in the ¹H-NMR spectrum, a ratio of an integrated valueof the peak to a sum of the integrated value of the peak, an integratedvalue of a peak of a hydrogen atom of the —CH₂— group, and an integralvalue of a peak of a hydrogen atom of the —CH< group may be 50% or more,80% or more, 85% or more, or 90% or more.

(3) In (1) or (2) above, the polymer compound may contain a repeatingstructure of oxy C₂₋₄ alkylene units.

(4) A lead-acid battery including a positive electrode plate, a negativeelectrode plate, and an electrolyte solution,

in which the negative electrode plate includes a negative electrodematerial, and

the negative electrode material contains a polymer compound having arepeating structure of oxy C₂₋₄ alkylene units.

(5) In (3) or (4) above, the polymer compound may contain at least oneselected from the group consisting of an etherified product of a hydroxycompound having a repeating structure of the oxy C₂₋₄ alkylene units andan esterified product of a hydroxy compound having the repeatingstructure of the oxy C₂₋₄ alkylene units, and

the hydroxy compound may be at least one selected from the groupconsisting of a poly C₂₋₄ alkylene glycol, a copolymer having arepeating structure of oxy C₂₋₄ alkylene, and a C₂₋₄ alkylene oxideadduct of a polyol.

(6) A lead-acid battery including a positive electrode plate, a negativeelectrode plate, and an electrolyte solution,

in which the negative electrode plate includes a negative electrodematerial,

the negative electrode material contains a polymer compound,

the polymer compound contains at least one selected from the groupconsisting of an etherified product of a hydroxy compound having arepeating structure of oxy C₂₋₄ alkylene units and an esterified productof a hydroxy compound having the repeating structure of the oxy C₂₋₄alkylene units, and

the hydroxy compound is at least one selected from the group consistingof a poly C₂₋₄ alkylene glycol, a copolymer having a repeating structureof oxy C₂₋₄ alkylene, and a C₂₋₄ alkylene oxide adduct of a polyol.

(7) In (5) or (6) above, the etherified product may have an —OR² group(wherein R² is an organic group) in which an —OH group at a terminal ofat least a part of the hydroxy compound is etherified, and the organicgroup R² may be a hydrocarbon group.

(8) In (5) or (6) above, the esterified product may have an —O—C(═O)—R³group (wherein R³ is an organic group) in which an —OH group at aterminal of at least a part of the hydroxy compound is esterified, andthe organic group R³ may be a hydrocarbon group.

(9) In (7) or (8) above, the hydrocarbon group may be an aliphatichydrocarbon group.

(10) In (9) above, the aliphatic hydrocarbon group may be either linearor branched.

(11) In (9) or (10) above, the number of carbon atoms of the aliphatichydrocarbon group is, for example, 30 or less, and may be 26 or less or22 or less, 20 or less or 16 or less, 14 or less or 10 or less, or 8 orless or 6 or less.

(12) In any one of (9) to (11) above, the aliphatic hydrocarbon groupmay be an alkyl group or an alkenyl group.

(13) In (12) above, the number of carbon atoms of the alkyl group may be1 or more, and the number of carbon atoms of the alkenyl group may be 2or more.

(14) In (12) or (13) above, the alkyl group may be at least one selectedfrom the group consisting of methyl, ethyl, n-propyl, i-propyl, n-butyl,i-butyl, s-butyl, t-butyl, n-pentyl, neopentyl, i-pentyl, s-pentyl,3-pentyl, t-pentyl, n-hexyl, 2-ethylhexyl, n-octyl, n-decyl, i-decyl,lauryl, myristyl, cetyl, stearyl, and behenyl.

(15) In (12) or (13) above, the alkenyl group may be, for example, aC₂₋₃₀ alkenyl group or a C₂₋₂₆ alkenyl group, a C₂₋₂₂ alkenyl group or aC₂₋₂₀ alkenyl group, or a C₁₀₋₂₀ alkenyl group.

(16) In (12), (13), or (15) above, the alkenyl group may be at least oneselected from the group consisting of vinyl, 1-propenyl, allyl,palmitoleyl, and oleyl.

(17) In any one of (3) to (16) above, the repeating structure of the oxyC₂₋₄ alkylene units may contain at least a repeating structure ofoxypropylene units.

(18) In (17) above, a proportion of the oxypropylene unit in the polymercompound (1 molecule) may be 5 mol % or more, 10 mol % or more, or 20mol % or more.

(19) In any one of (1) to (18) above, the polymer compound may contain acompound having Mn of 500 or more, a compound having Mn of 600 or more,or a compound having Mn of 1,000 or more.

(20) In (19) above, the Mn of the compound may be 20,000 or less, 15,000or less, 10,000 or less, 5,000 or less, 4,000 or less, or 3,000 or less.

(21) In any one of (1) to (18) above, the polymer compound may containat least a compound having Mn of 1,000 or more.

(22) In (21) above, the Mn of the compound may be 1,000 or more and20,000 or less, 1,000 or more and 15,000 or less, 1,000 or more and10,000 or less, 1000 or more and 5,000 or less, 1,000 or more and 4,000or less, or 1,000 or more and 3,000 or less.

(23) In any one of (1) to (22) above, a content of the polymer compoundin the negative electrode material may be more than 8 ppm, 13 ppm ormore, 15 ppm or more, 16 ppm or more, 50 ppm or more, or 80 ppm or moreon a mass basis.

(24) In any one of (1) to (23) above, a content of the polymer compoundin the negative electrode material may be less than 400 ppm, 360 ppm orless, 350 ppm or less, 240 ppm or less, 200 ppm or less, 165 ppm orless, or 164 ppm or less on a mass basis.

(25) In any one of (1) to (24) above, the electrolyte solution maycontain the polymer compound.

(26) In (25) above, a concentration of the polymer compound in theelectrolyte solution may be 500 ppm or less, 300 ppm or less, or 200 ppmor less on a mass basis.

(27) In (25) or (26) above, the concentration of the polymer compound inthe electrolyte solution may be 1 ppm or more, or 5 ppm or more on amass basis.

(28) In (25) above, the concentration of the polymer compound in theelectrolyte solution may be 100 ppm or more, may be 200 ppm or more or500 ppm or more, may be more than 500 ppm, or may be 600 ppm or more ona mass basis.

(29) In (28) above, the concentration of the polymer compound in theelectrolyte solution may be 5,000 ppm or less, 4,000 ppm or less, 3,000ppm or less, 2,500 ppm or less, or 2,400 ppm or less on a mass basis.

(30) In any one of (1) to (25) above, the electrolyte solution maycontain the polymer compound, the content of the polymer compound in thenegative electrode material may be 15 ppm or more and 360 ppm or less,and the concentration of the polymer compound in the electrolytesolution may be 500 ppm or less on a mass basis.

(31) In (30) above, the polymer compound may contain at least a compoundhaving Mn of 500 or more (or 600 or more, preferably 1,000 or more).

(32) In (25) above, the Mn of the compound may be 5,000 or less, 4,000or less, or 3,000 or less.

(33) In any one of (1) to (29) above, the electrolyte solution maycontain the polymer compound, the concentration of the polymer compoundin the electrolyte solution may be 100 ppm or more, and the polymercompound may contain at least a compound having Mn of 1,000 or more and5,000 or less (for example, 4,000 or less or 3,000 or less).

(34) In any one of (1) to (33) above, the negative electrode materialmay further contain an organic expander.

(35) In (34) above, the organic expander (or the negative electrodematerial) may contain a first organic expander having a sulfur elementcontent of 2,000 μmol/g or more or 3,000 μmol/g or more.

(36) In (35) above, the sulfur element content of the first organicexpander may be 9,000 μmol/g or less, 8,000 μmol/g or less, or 7,000μmol/g or less.

(37) In (25) or (36) above, the first organic expander may contain acondensate containing a unit of an aromatic compound having asulfur-containing group, and the condensate may contain, as the unit ofthe aromatic compound, at least one selected from the group consistingof a unit of a bisarene compound and a unit of a monocyclic aromaticcompound.

(38) In (37) above, the condensate may contain the unit of the bisarenecompound and the unit of the monocyclic aromatic compound

(39) In (37) or (38) above, the unit of the monocyclic aromatic compoundmay include a unit of a hydroxyarene compound.

(40) In (37) above, the sulfur-containing group may contain at least oneselected from the group consisting of a sulfonic acid group and asulfonyl group.

(41) In any one of (34) to (39) above, the organic expander (or thenegative electrode material) may contain a second organic expanderhaving a sulfur element content of less than 2,000 μmol/g (or 1,000μmol/g or less or 800 μmol/g or less).

(42) In (41) above, the sulfur element content of the second organicexpander may be 400 μmol/g or more.

(43) In (41) above, a ratio of the first organic expander to a totalamount of the first organic expander and the second organic expander maybe 20% by mass or more or 25% by mass or more.

(44) In (41) or (43) above, the ratio of the first organic expander tothe total amount of the first organic expander and the second organicexpander may be 80% by mass or less or 75% by mass or less.

(45) In any one of (34) to (44) above, the content of the organicexpander contained in the negative electrode material may be 0.01% bymass or more or 0.05% by mass or more.

(46) In any one of (34) to (45) above, the content of the organicexpander contained in the negative electrode material may be 1.0% bymass or less or 0.5% by mass or less.

(47) In any one of (1) to (46) above, the negative electrode materialmay contain carbonaceous material.

(48) In (47) above, the content of the carbonaceous material in thenegative electrode material may be 0.05% by mass or more or 0.10% bymass or more.

(49) In (47) or (48) above, the content of the carbonaceous material inthe negative electrode material may be 5% by mass or less or 3% by massor less.

(50) In any one of (1) to (49) above, the negative electrode materialmay contain barium sulfate.

(51) In (50) above, the content of the barium sulfate in the negativeelectrode material may be 0.05% by mass or more or 0.10% by mass ormore.

(52) In (50) or (51) above, the content of barium sulfate in thenegative electrode material may be 3% by mass or less or 2% by mass orless.

Example

Hereinafter, the present invention will be specifically described on thebasis of examples and comparative examples, but the present invention isnot limited to the following examples.

<<Lead-acid batteries E1 to E2 and R1>>

(1) Preparation of Lead-Acid Battery (a) Preparation of NegativeElectrode Plate

A lead powder as a raw material, barium sulfate, carbon black, a polymercompound (polypropylene glycol, Mn=2,000), and an organic expander shownin Table 1 are mixed with an appropriate amount of a sulfuric acidaqueous solution to obtain a negative electrode paste. At this time, thecomponents are mixed so that the content of the polymer compound in thenegative electrode material (solid of the negative electrode paste),which is determined by the procedure described above, is the value shownin Table 1, the content of barium sulfate is 0.6% by mass, the contentof carbon black is 0.3% by mass, and the content of the organic expanderis 0.1% by mass. A mesh portion of an expanded grid made of a Pb—Ca—Snalloy is filled with the negative electrode paste, which is then curedand dried to obtain a non-formed negative electrode plate.

As the organic expander, the following expanders are used.

(e1): Condensate of bisphenol compound having sulfonic acid groupintroduced and formaldehyde (sulfur element content: 5,000 μmol/g,Mw=9,600)

(e2): Condensate of bisphenol S compound having sulfonic acid groupintroduced and phenol sulfonic acid with formaldehyde (sulfur elementcontent: 4,000 μmol/g, Mw=8,000

(b) Preparation of Positive Electrode Plate

Lead powder as raw material is mixed with a sulfuric acid aqueoussolution to obtain a positive electrode paste. A mesh portion of anexpanded grid made of a Pb—Ca—Sn alloy is filled with the positiveelectrode paste, which is then cured and dried to obtain a non-formedpositive electrode plate.

(c) Preparation of Test Battery

A test battery has a rated voltage of 2 V and a rated 5-hour ratecapacity of 32 Ah. An element of the test battery includes sevenpositive electrode plates and seven negative electrode plates. Thenegative electrode plate is housed in a bag-shaped separator formed of apolyethylene microporous film, and alternately stacked with the positiveelectrode plate to form the element. The element is housed in apolypropylene container together with an electrolyte solution (sulfuricacid aqueous solution), and subjected to formation in the container toprepare a flooded-type lead-acid battery. The specific gravity of theelectrolyte solution after formation is 1.28 (in terms of 20° C.). Inthe lead-acid batteries E1 to E2, the concentration of the polymercompound in the electrolyte solution determined by the proceduredescribed above is 296 ppm or less.

In the ¹H-NMR spectrum of the polymer compound measured by the proceduredescribed above, a peak derived from —CH₂— of the oxypropylene unit isobserved in a chemical shift range of 3.2 ppm or more and 3.42 ppm orless, and a peak derived from —CH< and —CH₂— of the oxypropylene unit isobserved in a chemical shift range of more than 3.42 ppm and 3.8 ppm orless. In addition, in the ¹H-NMR spectrum, a ratio of an integratedvalue of the peak of 3.2 ppm to 3.8 ppm to the sum of the integratedvalue of this peak, an integrated value of a peak of hydrogen atoms ofthe —CH₂— group bonded to the oxygen atom, and an integrated value of apeak of a hydrogen atom of the —CH< group bonded to the oxygen atom is98.1%.

(2) Evaluation (a) Amount of Overcharge

Using the lead-acid battery, evaluation is performed under the followingconditions.

In order to set a more overcharge condition than the normal 4-10 mintest specified in JIS D 5301, a test of 1 minute of discharge and 10minutes of charge (1-10 min test) is performed at 75° C.±3° C. (hightemperature light load test). The high temperature light load test isperformed by repeating 1220 cycles of charge and discharge in the hightemperature light load test. The amount of overcharge (amount ofcharge-discharge capacity) in each cycle up to 1220 cycles is summed andaveraged to obtain the amount of overcharge (Ah) per cycle. The amountof overcharge is evaluated by a ratio (%) when the amount of overcharge(Ah) per cycle of the lead-acid battery R1 is 100.

Discharge: 25 A, 1 minute

Charge: 2.47 V/cell, 25 A, 10 minutes

Water tank temperature: 75° C.±3° C.

(b) Low Temperature HR Discharge Performance after Light Load Test

The test battery after full charge after the high temperature light loadtest in (a) above is discharged at a discharge current of 150 A at −15°C.±1° C. until the terminal voltage reaches 1.0 V/cell, and a dischargetime (low temperature HR discharge duration time after light load test)(s) at this time is obtained. The longer the discharge duration time,the better the low temperature HR discharge performance. The lowtemperature HR discharge performance of each battery is evaluated by aratio (%) when the discharge duration time of the lead-acid battery R1is 100.

(c) Charge Acceptability

A 10 second electric quantity is measured using the test battery afterfull charge. Specifically, the test battery is discharged at 6.4 A for30 minutes and left for 16 hours. Thereafter, the test battery ischarged at a constant current and a constant voltage of 2.42 V/cellwhile the upper limit of the current is 200 A, and an integratedelectric quantity for 10 seconds (10 second electric quantity) at thistime is measured. Both operations are performed in a water tank at 25°C.±2° C.

<<Lead-Acid Batteries R2-1, R2-2, R3-1 and R3-2>>

When the constituent components of the negative electrode paste aremixed, lignin sulfonate (sulfur element content is 600 μmol/g, Mw=5,500)or oil is added in place of the polymer compound so that the content inthe negative electrode material is the value shown in Table 1. Exceptfor this, a test battery is prepared and evaluated in the same manner asin the lead-acid battery E1. As the oil, a paraffin-based oil is used.Neither the paraffin-based oil nor the lignin sulfonate has a peak in arange of 3.2 ppm or more and 3.8 ppm or less in a chemical shift of a¹H-NMR spectrum measured using deuterated chloroform as a solvent.

The results of the lead-acid batteries E1 to E2, R1, R2-1, R2-2, R3-1,and R3-2 are shown in Table 1.

TABLE 1 R1 E1 E2 R2-1 R2-2 R3-1 R3-2 Content (mass ppm) of polymercompound in 0 82 82 0 0 negative electrode material Organic expander e1(0.1) e1 (0.1) e2 (0.1) e1 (0.1) e1 (0.1) (content (mass %) in negativeelectrode material) Additive (content in negative electrode material)Lignin sulfonate Oil — — — 82 mass ppm 0.1 mass % 82 mass ppm 0.1 mass %Amount of overcharge (%) 100 76 74 100 86 101 82 Charge acceptability(%) 100 92 93 100 87 99 90 Low temperature HR discharge performance 100131 128 — 136 — 109 after light load test (%)

As shown in Table 1, in the lead-acid batteries E1 and E2, the amount ofovercharge can be effectively reduced even when the content of thepolymer compound in the negative electrode material is as very small as82 ppm. On the other hand, in the lead-acid battery R2-1 or R3-1 usinglignin sulfonate or oil, unlike the lead-acid batteries E1 and E2 usingthe polymer compound, the effect of reducing the amount of overcharge isnot observed at all. From this, it is considered that the polymercompound is in a state in which an interaction such as an adsorptionaction on lead or lead sulfate is different from that of ligninsulfonate or oil in the negative electrode material. As described above,even when a conventional organic additive (specifically, an organicadditive having no peak in the range of 3.2 ppm or more and 3.8 ppm orless in the chemical shift of the ¹H-NMR spectrum) is used instead ofthe polymer compound, the effect of reducing the amount of overchargecannot be obtained. Thus, in the lead-acid batteries R2-1 and R3-1, theeffect of suppressing the hydrogen generation during overcharge issmall, and the liquid decrease suppressing effect is small.

As indicated by R2-2 and R3-2, even in the case of using ligninsulfonate or oil, when the content in the negative electrode material islarge, the effect of reducing the amount of overcharge can be obtainedto some extent. However, when lignin sulfonate or oil is added to suchan extent that the effect of reducing the amount of overcharge isobtained, the charge acceptability is also deteriorated. That is, withthe conventional organic additive, it is difficult to suppress thedeterioration of the charge acceptability while reducing the amount ofovercharge. On the other hand, in the lead-acid batteries E1 and E2,although a high effect of reducing the amount of overcharge is obtained,the deterioration of the charge acceptability is suppressed, and highcharge acceptability can be secured. From this, it is considered that inthe negative electrode material, most of the surface of lead or leadsulfate is thinly covered with the polymer compound, and the hydrogenovervoltage in the negative electrode plate increases. It is consideredthat since the lead surface is thinly covered with the polymer compound,elution of lead sulfate is less likely to be inhibited, and therefore,the deterioration of the charge acceptability is suppressed in thelead-acid batteries E1 and E2. Therefore, as compared with the case ofusing other organic additives such as lignin sulfonate and oil, it canbe said that the effect of simultaneously achieving the effect ofreducing the amount of overcharge and the effect of suppressing thedeterioration of the charge acceptability is enhanced in the case ofusing the polymer compound.

In the lead-acid batteries E1 and E2, as compared with the lead-acidbattery R1, high low temperature HR discharge performance can be securedeven after the high temperature light load test. This is considered tobe because the uneven distribution of the polymer compound in the leadpores is suppressed, so that ions easily move, the generation ofhydrogen gas during overcharge is suppressed, and the structural changeof the negative active material due to the collision of hydrogen gas isreduced.

<<Lead-Acid Batteries E3 to E9>>

The components are mixed so that the content of the polymer compound inthe negative electrode material is the value shown in Table 2. Exceptfor this, a test battery is prepared and evaluated in the same manner asin the lead-acid battery E 1. In the lead-acid batteries E3 to E9, theconcentration of the polymer compound in the electrolyte solutiondetermined by the procedure described above is 296 ppm or less.

The results of the lead-acid batteries E3 to E9 are shown in Table 2.The results of the lead-acid batteries E1 and R1 are also shown in Table2.

TABLE 2 R1 E3 E4 E1 E5 E6 E7 E8 E9 Content (mass ppm) of polymercompound in 0 8 16 82 164 200 300 350 400 negative electrode materialAmount of overcharge (%) 100 99 95 76 54 48 44 42 41 Chargeacceptability (%) 100 100 98 92 74 67 58 55 51 Low temperature HRdischarge performance after 100 101 107 131 118 114 98 81 16 light loadtest (%)

As shown in Table 2, inclusion of the polymer compound in the negativeelectrode material provides an excellent effect of reducing the amountof overcharge. In the lead-acid batteries R2-2 and R3-2 in Table 1, evenwhen 0.1% by mass of lignin sulfonate or oil is added, the amount ofovercharge decreases only to 82% or 86% of R1. On the other hand, asshown in the results of the lead-acid batteries E1 and E3 to E9, evenwhen a very small amount of the polymer compound is contained in thenegative electrode material, the effect of reducing the amount ofovercharge is obtained. Although the content of the polymer compound ishalf or less of the content of the additive in the lead-acid batteriesR2-2 and R3-2, the amount of overcharge can be reduced to 41% of R1.From the viewpoint of obtaining a higher effect of reducing the amountof overcharge, the content of the polymer compound in the negativeelectrode material is preferably more than 8 ppm. From the viewpoint ofsecuring a higher low temperature HR discharge performance, the contentof the polymer compound in the negative electrode material is preferablyless than 400 ppm by mass.

<<Lead-Acid Batteries E10 to E12>>

A polymer compound (polypropylene glycol) having Mn shown in Table 3 isused. Components of the negative electrode paste are mixed so that thecontent of the polymer compound in the negative electrode material(solid content of the negative electrode paste) is 82 ppm. Except forthese, a test battery is prepared and evaluated in the same manner as inthe lead-acid battery E1. For the polymer compound, in the ¹H-NMRspectrum, the ratio of the integrated value of the peak of 3.2 ppm to3.8 ppm to the sum of the integrated value of this peak, the integratedvalue of the peak of hydrogen atoms of the —CH₂— group bonded to theoxygen atom, and the integrated value of the peak of the hydrogen atomof the —CH< group bonded to the oxygen atom is 90.8% to 98.7%.

The results of the lead-acid batteries E10 to E12 are shown in Table 3.The results of the lead-acid batteries R1 and E1 are also shown in Table3.

TABLE 3 R1 E10 E11 E1 E12 Content (mass ppm) of polymer — 82 compound innegative electrode material Mn of polymer compound — 400 1000 2000 3000Amount of overcharge (%) 100 95 81 76 74 Charge acceptability (%) 100 9694 92 91 Low temperature HR discharge 100 101 123 131 134 performanceafter light load test (%)

As shown in Table 3, when the Mn of the polymer compound is 1,000 ormore, the effect of reducing the amount of overcharge is enhanced. Thisis considered to be because the polymer compound tends to remain in thenegative electrode material. In addition, when the Mn is 1,000 or more,excellent low temperature HR discharge performance after the hightemperature light load test can be secured. This is considered to bebecause by reducing the amount of overcharge, the structural change ofthe negative active material due to the collision of the hydrogen gaswith the negative active material is suppressed.

<<Lead-Acid Batteries E13-1 to E16-1 and E13-2 to E16-2>>

A polymer compound (polypropylene glycol) having Mn shown in Table 4 isadded to the negative electrode material and the electrolyte solution.The composition of the negative electrode paste is adjusted so that thecontent of the polymer compound in the negative electrode material(solid content of the negative electrode paste) determined by theprocedure described above is the value shown in Table 4. The polymercompound is added to the electrolyte solution so that the concentrationof the polymer compound in the electrolyte solution determined by theprocedure described above is the value shown in Table 4. Except forthese, a test battery is prepared in the same manner as in the lead-acidbattery E1, and the amount of overcharge is evaluated. The polymercompounds used in E13-1 to E16-1 are the same as the polymer compoundsused in E10, E11, E1 and E12, respectively. The polymer compounds usedin E13-2 to E16-2 are also the same as the polymer compounds used inE10, E11, E1 and E12, respectively.

The results of the lead-acid batteries E13-1 to E16-1 and E13-2 to E16-2are shown in Table 4. The results of the lead-acid battery R1 are alsoshown in Table 4.

TABLE 4 R1 E13-1 E14-1 E15-1 E16-1 E13-2 E14-2 E15-2 E16-2 Content (massppm) of polymer compound in — 31 62 negative electrode materialConcentration (mass ppm) of polymer — 1200 2400 compound in electrolytesolution Mn of polymer compound in negative — 400 1000 2000 3000 4001000 2000 3000 electrode material and electrolyte solution Amount ofovercharge (%) 100 96 77 85 83 83 77 79 51

As shown in Table 4, when the Mn of the polymer compound is 1,000 ormore, the effect of reducing the amount of overcharge is remarkablyenhanced. This is considered to be because the adsorptivity to lead isenhanced. In addition, it is considered that when the polymer compoundis contained in the electrolyte solution at a certain concentration,elution of the polymer compound from the negative electrode plate isalso suppressed.

<<Lead-Acid Batteries E17 to E19 and R4 to R6>>

A test battery is prepared in the same manner as the lead-acid batteryE1 except that an organic expander having a sulfur (S) element contentshown in Table 5 is used, and the amount of overcharge and the chargeacceptability are evaluated. The initial low temperature HR dischargeperformance is evaluated by the following procedure (d) using thelead-acid battery.

As the organic expander, the following expanders are used.

(e3): Lignin sulfonate (sulfur element content: 600 μmol/g, Mw=5,500)

(e4): Condensate of bisphenol compound having sulfonic acid groupintroduced and formaldehyde (sulfur element content: 3,000 μmol/g,Mw=9,000)

(e5): Condensate of bisphenol compound having sulfonic acid groupintroduced and formaldehyde (sulfur element content: 7,000 μmol/g,Mw=9,000)

As for the sulfur element content (μmol/g) in the organic expander,there is substantially no difference between a value before preparationof the negative electrode material and a value measured by disassemblingthe lead-acid battery and extracting each organic expander.

(d) Initial Low Temperature HR Discharge Performance

The test battery after full charge is discharged at a discharge currentof 150 A at −15° C. until the terminal voltage reaches 1.0 V/cell, andthe discharge time (initial low temperature HR discharge duration time)(s) at this time is obtained. The longer the discharge duration time,the better the low temperature HR discharge performance.

The initial low temperature HR discharge performance of the lead-acidbatteries R1 and E1 is also evaluated in accordance with the above.

The amount of overcharge and the initial low temperature HR dischargeperformance of each of the lead-acid batteries E17, E18, E1, and E19 areevaluated by a ratio (%) when data of each of the lead-acid batteriesR4, R5, R1, and R6 using the organic expander having the same sulfurelement content is 100.

The charge acceptability of each of the lead-acid batteries E17, E18,E1, and E19 is evaluated by a ratio (%) when the 10 second electricquantity of each of the lead-acid batteries R4, R5, R1, and R6 using anorganic expander having the same sulfur element content is 100.

The results of the lead-acid batteries E17 to E19 and R4 to R6 are shownin Table 5. The results of the lead-acid batteries R1 and E1 are alsoshown in Table 5.

TABLE 5 R4 E17 R5 E18 R1 E1 R6 E19 Content (mass ppm) of polymercompound in 0 82 0 82 0 82 0 82 negative electrode material Organicexpander e3 e4 e1 e5 S element content (μmol/g) of organic expander 6003000 5000 7000 Amount of overcharge (%) 100 75 100 75 100 76 100 75Charge acceptability (%) 100 85 100 92 100 92 100 95 Initial lowtemperature HR discharge 100 113 100 107 100 105 100 104 performance (%)

As shown in Table 5, when the polymer compound and the first organicexpander (preferably, an organic expander having a sulfur elementcontent of 3,000 μmol/g or more) are used in combination, thedeterioration of the charge acceptability is further suppressed. Whenthe first organic expander is used, the particle size of lead sulfategenerated during discharge is small and the specific surface area islarge as compared with the case of using an organic expander having asmall sulfur element content, so that lead sulfate is less likely to becoated with the polymer compound. As a result, it is considered that inthe case of using the first organic expander, the deterioration of thecharge acceptability is suppressed as compared with the case of using anorganic expander having a small sulfur element content.

When the second organic expander having a small sulfur element contentsuch as lignin sulfonate is used in combination with the polymercompound, the initial low temperature HR discharge performance isgreatly improved. This is considered to be because the particle size ofthe colloid formed in sulfuric acid by the second organic expander isreduced by the surfactant action of the polymer compound as comparedwith a case where the polymer compound is not used, so that thedischarge reaction easily proceeds. On the other hand, in the firstorganic expander having a high sulfur element content, even when thepolymer compound is not used, the particle size of the colloid to beproduced is small, and therefore, a change in particle size due toaddition of the polymer compound is small. Thus, it is considered thatan effect of improving the low temperature HR discharge performance isreduced.

<<Lead-Acid Batteries E20 to E24>>

The first organic expander and/or the second organic expander having asulfur (S) element content shown in Table 6 are mixed so that thecontent of each organic expander determined by the procedure describedabove is the value shown in Table 6. Except for these, a test battery isprepared similarly to the lead-acid battery E1, and the chargeacceptability is evaluated. As the first organic expander, the same (e1)as in the lead-acid battery E1 is used, and as the second organicexpander, the same lignin sulfonate (e3) as in the lead-acid battery E17is used. As for the sulfur element content (μmol/g) in the organicexpander, there is substantially no difference between a value beforepreparation of the negative electrode material and a value measured bydisassembling the lead-acid battery and extracting each organicexpander.

The charge acceptability of the lead-acid batteries E20 to E24 isevaluated by a ratio (%) when the 10 second electric quantity of thelead-acid battery E20 is 100.

The results of the lead-acid batteries E20 to E24 are shown in Table 6.

TABLE 6 E20 E21 E22 E23 E24 Content (mass ppm) of polymer 82 compound innegative electrode material First organic expander 0 0.05 0.1 0.15 0.2(S element content 5000 μmol g⁻¹) (mass %) Second organic expander 0.20.15 0.1 0.05 0 (S element content 600 μmol g⁻¹) (mass %) Chargeacceptability (%) 100 105 111 108 103

As shown in Table 6, when the polymer compound is used, high chargeacceptability is obtained by using both organic expanders incombination. The result when the first organic expander and the secondorganic expander are used in combination is superior to the value of thecharge acceptability assumed when each organic expander is used alone.From this, it can be said that when the polymer compound is used, asynergistic effect is obtained by using the first organic expander andthe second organic expander.

<<Lead-Acid Batteries E25 to E30>>

A test battery is prepared and evaluated similarly to the lead-acidbattery E1 except that the polymer compound shown in Table 7 is used.For the polymer compound, in the ¹H-NMR spectrum, the ratio of theintegrated value of the peak of 3.2 ppm to 3.8 ppm to the sum of theintegrated value of this peak, the integrated value of the peak ofhydrogen atoms of the —CH₂— group bonded to the oxygen atom, and theintegrated value of the peak of the hydrogen atom of the —CH< groupbonded to the oxygen atom is 97.6% to 99.7%.

The results of the lead-acid batteries E25 to E30 are shown in Table 7.The results of the lead-acid batteries R1 and E7 are also shown in Table7.

The charge acceptability of the lead-acid batteries E25 to E30 isevaluated by a ratio (%) when the 10 second electric quantity of thelead-acid battery R1 is 100.

TABLE 7 Content (mass ppm) of polymer compound Amount of Charge innegative Polymer compound overcharge acceptability electrode materialType Mn (%) (%) R1 0 — — 100 100 E7 300 Polypropylene glycol 2000 44 58E25 300 Polyoxyethylene polyoxypropylene butyl 1800 44 81 ether(oxypropylene unit 43 mol %) E26 300 Polyoxypropylene butyl ether 239055 85 E27 300 Polyoxyethylene polyoxypropylene hexylene 14000 37 54glycol ether (oxypropylene unit 20 mol %) E28 300 Polyoxypropylenemethyl ether 1800 45 78 E29 300 Polyoxypropylene ethyl ether 2200 45 77E30 300 Polyoxypropylene acetate 1900 45 76

As shown in Table 7, even when an etherified product or an esterifiedproduct of a hydroxy compound having the repeating structure of the oxyC₂₋₄ alkylene units is used, the deterioration of the chargeacceptability is suppressed while reducing the amount of overcharge.

INDUSTRIAL APPLICABILITY

The lead-acid battery according to one aspect of the present inventioncan be suitably used as, for example, a power source for starting avehicle (automobiles, motorcycles, etc.) and a power source for anindustrial energy storage apparatus or the like such as an electricvehicle (forklift, etc.). Note that these applications are merelyillustrative and not limited to these applications.

DESCRIPTION OF REFERENCE SIGNS

-   -   1: lead-acid battery    -   2: negative electrode plate    -   3: positive electrode plate    -   4: separator    -   5: positive electrode shelf portion    -   6: negative electrode shelf portion    -   7: positive pole    -   8: penetrating connection body    -   9: negative pole    -   11: element    -   12: container    -   13: partition    -   14: cell chamber    -   15: lid    -   16: negative electrode terminal    -   17: positive electrode terminal    -   18: vent plug

1. A lead-acid battery comprising a positive electrode plate, a negativeelectrode plate, and an electrolyte solution, wherein the negativeelectrode plate comprises a negative electrode material, the negativeelectrode material contains a polymer compound, and the polymer compoundhas a peak in a range of 3.2 ppm or more and 3.8 ppm or less in achemical shift of ¹H-NMR spectrum.
 2. The lead-acid battery according toclaim 1, wherein a content of the polymer compound in the negativeelectrode material is more than 8 ppm on a mass basis.
 3. The lead-acidbattery according to claim 1, wherein a content of the polymer compoundin the negative electrode material is less than 400 ppm on a mass basis.4. The lead-acid battery according to claim 1, wherein the polymercompound contains an oxygen atom bonded to a terminal group and a —CH₂—group and/or a —CH< group bonded to the oxygen atom, and in the ¹H-NMRspectrum, a ratio of an integrated value of the peak to a sum of theintegrated value of the peak, an integrated value of a peak of ahydrogen atom of the —CH₂— group, and an integrated value of a peak of ahydrogen atom of the —CH< group is 85% or more.
 5. The lead-acid batteryaccording to claim 1, wherein the polymer compound contains a repeatingstructure of oxy C₂₋₄ alkylene units.
 6. The lead-acid battery accordingto claim 5, wherein the polymer compound contains at least one selectedfrom the group consisting of an etherified product of a hydroxy compoundhaving a repeating structure of the oxy C₂₋₄ alkylene units and anesterified product of a hydroxy compound having the repeating structureof the oxy C₂₋₄ alkylene units, and the hydroxy compound is at least oneselected from the group consisting of a poly C₂₋₄ alkylene glycol, acopolymer having a repeating structure of oxy C₂₋₄ alkylene, and a C₂₋₄alkylene oxide adduct of a polyol.
 7. The lead-acid battery according toclaim 5, wherein the repeating structure of the oxy C₂₋₄ alkylene unitscontains at least a repeating structure of oxypropylene units.
 8. Thelead-acid battery according to claim 1, wherein the electrolyte solutioncontains the polymer compound, the content of the polymer compound inthe negative electrode material is 15 ppm or more and 360 ppm or less,and the concentration of the polymer compound in the electrolytesolution is 500 ppm or less on a mass basis.
 9. The lead-acid batteryaccording to claim 8, wherein the polymer compound contains at least acompound having a number average molecular weight of 1,000 or more. 10.The lead-acid battery according to claim 1, wherein the electrolytesolution contains the polymer compound, the concentration of the polymercompound in the electrolyte solution is 100 ppm or more, and the polymercompound contains at least a compound having a number average molecularweight of 1,000 or more and 5,000 or less.
 11. The lead-acid batteryaccording to claim 1, wherein the negative electrode material furthercontains a first organic expander having a sulfur element content of2,000 μmol/g or more.
 12. The lead-acid battery according to claim 11,wherein the first organic expander contains a condensate containing aunit of an aromatic compound having a sulfur-containing group, and thecondensate contains, as the unit of the aromatic compound, at least oneselected from the group consisting of a unit of a bisarene compound anda unit of a monocyclic aromatic compound.
 13. The lead-acid batteryaccording to claim 12, wherein the condensate contains the unit of thebisarene compound and the unit of the monocyclic aromatic compound. 14.The lead-acid battery according to claim 12, wherein the unit of themonocyclic aromatic compound includes a unit of a hydroxyarene compound.15. The lead-acid battery according to claim 1, wherein the negativeelectrode material further contains a second organic expander having asulfur element content of less than 2,000 μmol/g.
 16. A lead-acidbattery comprising a positive electrode plate, a negative electrodeplate, and an electrolyte solution, wherein the negative electrode platecomprises a negative electrode material, and the negative electrodematerial contains a polymer compound having a repeating structure of oxyC₂₋₄ alkylene units.
 17. The lead-acid battery according to claim 16,wherein a content of the polymer compound in the negative electrodematerial is more than 8 ppm on a mass basis.
 18. The lead-acid batteryaccording to claim 16, wherein a content of the polymer compound in thenegative electrode material is less than 400 ppm on a mass basis. 19.The lead-acid battery according to claim 16, wherein the polymercompound contains an oxygen atom bonded to a terminal group and a —CH₂—group and/or a —CH< group bonded to the oxygen atom, and in the ¹H-NMRspectrum, a ratio of an integrated value of the peak to a sum of theintegrated value of the peak, an integrated value of a peak of ahydrogen atom of the —CH₂— group, and an integrated value of a peak of ahydrogen atom of the —CH< group is 85% or more.
 20. The lead-acidbattery according to claim 16, wherein the polymer compound contains atleast one selected from the group consisting of an etherified product ofa hydroxy compound having a repeating structure of the oxy C₂₋₄ alkyleneunits and an esterified product of a hydroxy compound having therepeating structure of the oxy C₂₋₄ alkylene units, and the hydroxycompound is at least one selected from the group consisting of a polyC₂₋₄ alkylene glycol, a copolymer having a repeating structure of oxyC₂₋₄ alkylene, and a C₂₋₄ alkylene oxide adduct of a polyol. 21-29.(canceled)